Bergey's Manual of Systematic Bacteriology and Determinative Bacteriology

Bergey’s manual of determinative bacteriology is a classic and comprehensive reference book that provides a systematic and detailed description of the different groups of bacteria. It is widely used by microbiologists, biologists, medical professionals, and students to identify and classify unknown bacterial isolates based on their phenotypic characteristics, such as morphology, staining, biochemical reactions, oxygen requirements, and motility.

The manual was first published in 1923 by David Hendricks Bergey, an American bacteriologist and professor at the University of Pennsylvania. He was the editor-in-chief of the first four editions of the manual, which were published between 1923 and 1948. The manual was named after him in recognition of his contributions to the field of bacteriology.

The manual has undergone several revisions and updates since its first publication. The most recent edition is the ninth edition, which was published in 1994 and reprinted in 2000. The ninth edition consists of one volume that covers 35 groups of bacteria, divided into four major categories based on their cell wall composition: Gracilicutes (gram-negative bacteria), Firmicutes (gram-positive bacteria other than actinomycetes), Tenericutes (bacteria lacking cell wall other than actinomycetes), and Mendosicutes (bacteria lacking peptidoglycan in their cell wall like archaea).

The manual does not follow a phylogenetic approach to classify bacteria, but rather a phenetic approach that relies on observable traits. The manual does not attempt to reflect the evolutionary relationships among bacteria, but rather to provide practical schemes for identification. The manual also does not include all the known bacterial species, but only those that are of practical importance or interest in medicine, industry, agriculture, or ecology.

The manual is organized into parts, sections, genera, families, and orders. Each part corresponds to one of the four major categories of bacteria. Each section corresponds to a group of bacteria that share some common features. Each genus corresponds to a group of closely related species that have similar characteristics. Some genera are grouped into families or orders based on their phylogenetic or taxonomic affinities.

The manual provides a brief introduction to each part and section, followed by a key for identification. The key consists of a series of dichotomous questions that lead to the identification of a genus or a family. The key is based on simple tests that can be performed in the laboratory using standard methods and equipment. The key also provides references to other sources of information for further identification.

The manual also provides a description of each genus or family, including its morphology, physiology, ecology, distribution, pathogenicity, and significance. The description also includes representative species and their characteristics. The description is accompanied by illustrations or photographs that show the typical appearance of the cells or colonies.

The manual is a valuable resource for anyone who wants to learn more about the diversity and classification of bacteria. It is also a useful tool for anyone who needs to identify unknown bacterial cultures in various settings. However, the manual is not intended to be a definitive authority on bacterial taxonomy or nomenclature. The manual reflects the state of knowledge at the time of its publication and may not include some recent discoveries or changes in bacterial classification. Therefore, users should consult other sources of information for confirmation or clarification when necessary.

Bergey’s Manual of Determinative Bacteriology was first published in 1923 by David Hendricks Bergey, who was the chairman of the Society of American Bacteriologists. The manual aimed to provide a concise and authoritative guide for the identification of bacteria based on their phenotypic characteristics, such as morphology, staining, biochemical reactions, and serological tests. The manual did not attempt to classify bacteria according to their evolutionary relationships, but rather grouped them into convenient categories for practical purposes.

The manual was revised and updated periodically by the editorial board of the Society of American Bacteriologists (later renamed as the American Society for Microbiology). The manual went through nine editions from 1923 to 1994, each edition reflecting the advances in bacteriological knowledge and techniques at the time. The manual was widely used by microbiologists, clinicians, students, and teachers as a reliable and comprehensive reference for bacterial identification.

The ninth and last edition of Bergey’s Manual of Determinative Bacteriology was published in 1994 and reprinted in 2000. It contained 35 sections that covered all the known groups of bacteria at that time. The manual used a polyphasic approach that combined phenotypic, genotypic, and phylogenetic data to assign bacteria to different taxa. The manual also included tables, keys, diagrams, and illustrations to facilitate the identification process.

The ninth edition of Bergey’s Manual of Determinative Bacteriology was the final edition of this series, as the editorial board decided to shift the focus from determinative to systematic bacteriology in the subsequent editions. The new series, called Bergey’s Manual of Systematic Bacteriology, aimed to present a more natural and accurate classification of bacteria based on their phylogenetic relationships, as revealed by molecular methods such as DNA sequencing and ribosomal RNA analysis. The new series also provided more information on the ecology, physiology, pathogenicity, and diversity of bacteria. The first edition of Bergey’s Manual of Systematic Bacteriology was published in four volumes from 1984 to 1989, and the second edition was published in five volumes from 2001 to 2012.

The first edition of Bergey’s Manual of Systematic Bacteriology was published in four volumes from 1984 to 1989 . It was an attempt to organize bacterial species according to known phylogenetic relationships, rather than phenotypic characteristics as in the previous editions of Bergey’s Manual of Determinative Bacteriology . The first edition of Bergey’s Manual of Systematic Bacteriology was aimed at undergraduates, graduate students, researchers, professors and experienced professionals at all levels. It provided comprehensive and authoritative descriptions of bacteria and archaea through the collaboration of nearly one thousand microbiologists from all over the world .

The first edition of Bergey’s Manual of Systematic Bacteriology divided bacteria into four divisions (or phyla) based on the characteristics of cell wall: Gracilicutes (gram-negative cell wall), Firmicutes (gram-positive cell wall other than actinomycetes), Tenericutes (bacteria lacking cell wall other than actinomycetes) and Mendosicutes (bacteria lacking peptidoglycan in their cell wall like Archaea). Each division was further subdivided into sections based on such features as gram stain reactions, cell shape, cell arrangements, oxygen requirement, motility, and nutritional and metabolic properties. Each section consisted of a number of genera, some of which were grouped into families and orders.

The four volumes of the first edition of Bergey’s Manual of Systematic Bacteriology contained the bacteria considered to be of practical importance in medicine or those that illustrated biologically unusual or interesting principles. The four volumes were:

• Volume 1: It included gram-negative bacteria (sections 1-11) (1984) .
• Volume 2: It included gram-positive bacteria, phototrophic and other specialized bacteria including gliding bacteria (sections 12-17) (1986) .
• Volume 3: It included bacteria with unusual cell wall like Archaea (sections 18-25) (1989) .
• Volume 4: It included Actinomycetes and other filamentous bacteria (sections 26-33) (1991) .

The first edition of Bergey’s Manual of Systematic Bacteriology was a landmark in the field of prokaryotic biology and a valuable resource for microbiologists. However, it became outdated due to the rapid advances in DNA sequencing technology and phylogenetic analysis that revealed new insights into the evolutionary relationships among prokaryotes. Therefore, a second edition was published in five volumes from 2001 to 2012, which reflected the current thinking and advances in the field.

Bergey’s Manual of Systematic Bacteriology is a comprehensive reference work that provides detailed descriptions and classifications of bacteria based on their phylogenetic relationships. Phylogeny is the study of the evolutionary history and relatedness of organisms. Unlike the determinative manual, which groups bacteria by their observable characteristics, the systematic manual groups bacteria by their genetic similarities and differences.

The systematic manual is divided into four main divisions or phyla, which are further subdivided into classes, orders, families, genera, and species. The four divisions are:

• Gracilicutes: These are bacteria with gram-negative cell walls, which are thin and easily stained by the Gram stain technique. They include many diverse groups of bacteria, such as proteobacteria, cyanobacteria, spirochetes, and chlamydiae.
• Firmicutes: These are bacteria with gram-positive cell walls, which are thick and resist staining by the Gram stain technique. They include many common and medically important bacteria, such as staphylococci, streptococci, bacilli, and clostridia.
• Tenericutes: These are bacteria that lack cell walls or have very reduced cell walls. They include the mycoplasmas, which are the smallest and simplest bacteria known. They are often parasites or pathogens of plants and animals.
• Mendosicutes: These are bacteria that have cell walls that lack peptidoglycan, the main component of most bacterial cell walls. They include the archaea, which are ancient and diverse bacteria that live in extreme environments, such as hot springs, salt lakes, and deep-sea vents.

Each division is further divided into sections based on various criteria, such as morphology, metabolism, ecology, and molecular characteristics. Each section contains one or more genera of bacteria that share common features. Each genus contains one or more species of bacteria that have distinct characteristics and can be distinguished from other species.

The systematic manual provides detailed information on each bacterial group, such as their morphology, physiology, biochemistry, genetics, ecology, pathogenicity, and diversity. It also provides references to the scientific literature and other sources of information for further study. The systematic manual is updated regularly to reflect the latest advances in bacterial taxonomy and phylogeny.

The systematic manual is intended for researchers and students who are interested in the diversity and evolution of bacteria. It is not designed for practical identification of unknown bacterial cultures. For that purpose, the determinative manual is more suitable and user-friendly. However, the systematic manual can provide valuable insights into the relationships and characteristics of different bacterial groups and help understand their roles in nature and human health.

Bergey`s manual of determinative bacteriology uses a classification system based on phenotypic characteristics, such as cell wall composition, morphology, differential staining, oxygen requirement, and biochemical testing. The manual does not attempt to reflect the evolutionary relationships among bacteria, but rather provides practical schemes for identifying unknown bacterial cultures.

The manual divides bacteria into four major divisions (or phyla), according to the characteristics of their cell walls. These are:

• Gracilicutes: bacteria with thin gram-negative cell walls
• Firmicutes: bacteria with thick gram-positive cell walls, except for the actinomycetes
• Tenericutes: bacteria lacking cell walls, except for the actinomycetes
• Mendosicutes: bacteria with unusual cell walls, such as the archaea

Each division is further subdivided into sections based on other phenotypic features, such as gram stain reaction, cell shape, cell arrangement, oxygen requirement, motility, and nutritional and metabolic properties. Each section consists of a number of genera, which may or may not be grouped into families and orders.

The manual assigns each bacterial group a number from 1 to 35, which serves as a convenient way to refer to them. For example, group 1 includes the spirochetes, group 17 includes the gram-positive cocci, and group 31 includes the methanogens.

The manual also provides detailed descriptions of each bacterial group, including their morphology, physiology, ecology, pathogenicity, and culture methods. It also includes tables and flowcharts to help with the identification process.

The manual is designed to be used in conjunction with other sources of information, such as molecular techniques and reference collections. It is not intended to be a definitive or comprehensive classification of bacteria, but rather a useful tool for practical purposes.

The second edition of Bergey’s manual of systematic bacteriology is a major revision of the first edition, which was published in four volumes from 1984 to 1989. The second edition reflects the advances in molecular biology and phylogenetic analysis that have reshaped the field of bacterial taxonomy in the past two decades. The second edition is published in five volumes from 2001 to 2012, and covers all known prokaryotic taxa, including many newly described species and genera. The second edition also includes more ecological and clinical information about individual taxa, as well as updated references and illustrations.

The second edition does not group all the clinically important prokaryotes together as the first edition did; instead, pathogenic species are placed phylogenetically and thus scattered throughout the following five volumes:

• Volume 1: The Archaea and the deeply branching and phototrophic bacteria (2001)
• Volume 2: The Proteobacteria (2005)
• Volume 3: The Firmicutes (2009)
• Volume 4: The Bacteroidetes, Spirochaetes, Tenericutes (Mollicutes), Acidobacteria, Fibrobacteres, Fusobacteria, Dictyoglomi, Gemmatimonadetes, Lentisphaerae, Verrucomicrobia, Chlamydiae, and Planctomycetes (2010)
• Volume 5: The Actinobacteria (2012)

The second edition uses a phylogenetic framework based on 16S rRNA gene sequences and other molecular markers to classify bacteria into phyla, classes, orders, families, genera, and species. The second edition also recognizes that bacterial diversity is not fully captured by the current classification system, and introduces the concept of candidate phyla for those groups of bacteria that have not been cultured or formally described yet. The second edition also acknowledges the existence of horizontal gene transfer and genomic variation among bacterial populations, and discusses the implications for bacterial systematics.

The second edition of Bergey’s manual of systematic bacteriology is a comprehensive and authoritative reference for microbiologists, biologists, medical professionals, and students who are interested in the diversity and evolution of prokaryotes. It is also a valuable resource for identifying and characterizing bacterial isolates using phenotypic and molecular methods. The second edition is available in print and online formats.

The third edition of Bergey`s manual is currently in progress and is expected to be completed by 2024. It will be published by Springer Nature and will consist of 12 volumes. The third edition will reflect the advances in molecular phylogeny and genomics that have revolutionized the field of bacterial taxonomy and classification. It will also incorporate new information on bacterial ecology, physiology, metabolism, and pathogenesis.

The third edition will adopt a phylogenetic framework based on the 16S rRNA gene sequence as the primary criterion for grouping bacteria into phyla, classes, orders, families, genera, and species. It will also use other molecular markers, such as whole-genome sequences, multilocus sequence analysis, and single-copy genes, to resolve the relationships among closely related taxa. The third edition will also consider phenotypic characteristics, such as cell morphology, staining properties, biochemical reactions, and antigenic profiles, to support the molecular classification and identification of bacteria.

The third edition will cover all known bacteria, including those that have not been cultured or named yet. It will also include new chapters on bacterial diversity, evolution, ecology, biotechnology, and human microbiome. The third edition will provide comprehensive descriptions of each bacterial taxon, including its history, nomenclature, phylogeny, morphology, physiology, metabolism, ecology, pathogenicity, and biotechnological potential. The third edition will also provide keys and tables for the identification of bacteria at different taxonomic levels.

The third edition of Bergey`s manual will be a valuable resource for microbiologists, biologists, medical professionals, environmental scientists, biotechnologists, and anyone interested in the diversity and significance of bacteria. It will be the most authoritative and comprehensive reference on bacterial taxonomy and classification available.

The 9th edition of Bergey’s manual of determinative bacteriology was published in 1994 and reprinted in 2000. It is a reference book that helps in the identification of unknown bacteria by using phenotypic characteristics, such as cell shape, size, Gram reaction, motility, oxygen requirement, metabolic properties, and habitat. It does not reflect the phylogenetic relationships among bacteria, which are presented in Bergey’s manual of systematic bacteriology.

In this edition, bacteria are divided into four major divisions (or phyla) based on the cell wall composition: Gracilicutes (Gram-negative cell wall), Firmicutes (Gram-positive cell wall other than actinomycetes), Tenericutes (bacteria lacking cell wall other than actinomycetes), and Mendosicutes (bacteria lacking peptidoglycan in their cell wall like Archaea). Each division is further subdivided into sections based on other morphological and physiological features. Each section contains a number of genera, which may or may not be grouped into families and orders. Each genus has a description, a list of synonyms and other nomenclatural changes, a key or table to species, and illustrations.

The first division, Gracilicutes, includes groups 1 to 16, which comprise various types of Gram-negative bacteria, such as spirochetes, sulfate and sulfur-reducing bacteria, rickettsias, chlamydias, anoxygenic and oxygenic phototrophic bacteria, aerobic chemolithotrophs, budding and appendaged bacteria, sheathed bacteria, non-photosynthetic and photosynthetic gliding bacteria.

The second division, Firmicutes, includes groups 17 to 29, which comprise various types of Gram-positive bacteria, such as cocci, endospore-forming rods and cocci, non-sporing rods, mycobacteria, non-cardiform actinomycetes, genera with multilocular sporangia, actinoplanes, streptomycetes and related genera.

The third division, Tenericutes, includes group 30, which comprises Mycoplasma and related genera that lack cell wall.

The fourth division, Mendosicutes, includes groups 31 to 35, which comprise various types of Archaea that lack peptidoglycan in their cell wall. These include methanogens, archaeal sulfate reducers, extremely halophiles, cell wall-less archaea, and extremely thermophilic and hyperthermophilic sulfur metabolizers.

This edition of Bergey’s manual of determinative bacteriology is useful for identifying unknown bacterial cultures based on their observable characteristics. However, it does not provide information on the evolutionary history or genetic diversity of bacteria. For that purpose, Bergey’s manual of systematic bacteriology is more suitable.

The most recent revision of Bergey’s manual is the 10th edition of Bergey’s Manual of Determinative Bacteriology, published in 1994 and reprinted in 2000. This edition is based on the data contained in the four-volume Bergey’s Manual of Systematic Bacteriology, which attempted to organize bacterial species according to known phylogenetic relationships. However, the determinative manual does not classify bacteria according to evolutionary relatedness but provides identification schemes, based on such criteria as cell wall composition, morphology, differential staining, oxygen requirement, and biochemical testing.

The 10th edition of Bergey’s Manual of Determinative Bacteriology divides bacteria into 35 groups under four major categories: Gracilicutes (gram-negative cell wall), Firmicutes (gram-positive cell wall other than actinomycetes), Tenericutes (bacteria lacking cell wall other than actinomycetes), and Mendosicutes (bacteria lacking peptidoglycan in their cell wall like Archaea). Each group consists of a number of genera, some of which are further grouped into families and orders. The manual also includes discussions of difficulties in identification, keys or tables to genera and species, genus descriptions, synonyms, other nomenclatural changes, and numerous illustrations.

The 10th edition of Bergey’s Manual of Determinative Bacteriology is a widely used reference for identifying unknown bacterial cultures. However, it is not up to date with the recent advances in molecular phylogeny and taxonomy of prokaryotes. Therefore, a new edition of Bergey’s Manual of Systematic Bacteriology is being published online since 2015, which reflects the current state of knowledge on the diversity and classification of Archaea and Bacteria. The new edition is divided into five volumes, each covering a major group of prokaryotes based on 16S rRNA gene sequences. The new edition also includes more ecological information about individual taxa and incorporates new genera and species described since the publication of the previous edition.

Bergey’s Manual Trust is the organization that oversees the publication of Bergey’s manuals. The Trust was formed in 1936 to use the royalty income from the sale of the manuals to pay for the costs of preparing, editing and publishing revisions and successive editions as well as providing for research that may be necessary or desirable in such activities. The Trust consists of an Editorial Board and an Advisory Board, which are composed of eminent microbiologists from all over the world. The Trust also collaborates with other organizations and institutions to promote the study and dissemination of prokaryotic systematics.

Bergey’s manuals are essential tools for microbiologists, biologists, clinicians, and other professionals who need to identify or learn about prokaryotic organisms. They provide comprehensive and authoritative descriptions of bacteria and archaea using every characterizing aspect. They also offer a natural classification of prokaryotes that reflects their evolutionary history and relationships.

Gram-negative bacteria are those that have a thin layer of peptidoglycan in their cell wall and stain red or pink with the Gram stain. They are usually more resistant to antibiotics than gram-positive bacteria because they have an outer membrane that protects them from many substances. Gram-negative bacteria are divided into 16 groups in Bergey`s Manual of Determinative Bacteriology, based on their morphology, motility, oxygen requirements, metabolic characteristics, and other features. Some of the groups are:

• Group 1: Spirochetes. These are long, slender, helical bacteria that move by axial filaments. They are anaerobic or microaerophilic and can cause diseases such as syphilis and Lyme disease.
• Group 2: Sulfate- and sulfur-reducing bacteria. These are anaerobic bacteria that use sulfate or sulfur as terminal electron acceptors in their respiration. They produce hydrogen sulfide as a by-product and can be found in anaerobic environments such as sediments and sewage.
• Group 3: Rickettsias and chlamydias. These are obligate intracellular parasites that infect eukaryotic cells and depend on them for energy and nutrients. They are very small and have reduced genomes. They can cause diseases such as typhus, Rocky Mountain spotted fever, and chlamydia.
• Group 4: Anoxygenic phototrophic bacteria. These are bacteria that use light as an energy source but do not produce oxygen as a by-product. They use organic or inorganic compounds as electron donors for photosynthesis. They have various pigments that give them different colors and can be found in aquatic habitats.
• Group 5: Oxygenic phototrophic bacteria. These are bacteria that use light as an energy source and produce oxygen as a by-product. They use water as an electron donor for photosynthesis. They include cyanobacteria, which have chlorophyll a and phycobilins as pigments and can form colonies or filaments.
• Group 6: Aerobic chemolithotrophic bacteria. These are bacteria that use inorganic compounds such as ammonia, nitrite, hydrogen, or sulfur as energy sources and oxygen as a terminal electron acceptor. They can oxidize these compounds to produce energy and synthesize organic molecules from carbon dioxide. They play important roles in biogeochemical cycles such as nitrogen and sulfur cycles.
• Group 7: Budding and/or appendaged bacteria. These are bacteria that have unusual modes of cell division or growth. They may form buds or extensions from their cell surface that can detach or remain attached to the parent cell. They may also have stalks, prosthecae, or holdfasts that help them attach to surfaces or substrates.
• Group 8: Sheathed bacteria. These are bacteria that have a tubular or filamentous structure that is surrounded by a sheath or envelope of extracellular material. The sheath may protect the cells from predators or environmental stress or help them adhere to surfaces or substrates.
• Group 9: Non-photosynthetic non-fruiting gliding bacteria. These are bacteria that have the ability to glide over solid surfaces without the use of flagella or pili. They may secrete slime or polysaccharides that help them move or adhere to surfaces. They are not photosynthetic and do not form fruiting bodies like some other gliding bacteria.
• Group 10: Fruiting gliding bacteria. These are bacteria that have the ability to glide over solid surfaces without the use of flagella or pili. They are also able to form fruiting bodies, which are aggregates of cells that differentiate into spores under unfavorable conditions. The spores can survive harsh environments and germinate when conditions improve.

These are some examples of the gram-negative bacteria groups in Bergey`s Manual of Determinative Bacteriology. There are more groups that have different characteristics and ecological roles.

Gram-positive bacteria are a diverse group of prokaryotes that have a thick cell wall composed of peptidoglycan and stain purple with the Gram stain. They include many medically and industrially important genera, such as Staphylococcus, Streptococcus, Bacillus, Clostridium, Listeria, Corynebacterium, and Mycobacterium. They also include some of the most ancient and unusual bacteria, such as the actinomycetes and the thermophilic and acidophilic bacteria.

In Bergey`s Manual of Systematic Bacteriology, gram-positive bacteria are divided into two phyla: Firmicutes and Actinobacteria. The Firmicutes comprise low G+C gram-positive bacteria, which have a DNA base composition of less than 50% guanine plus cytosine. The Actinobacteria comprise high G+C gram-positive bacteria, which have a DNA base composition of more than 50% guanine plus cytosine. The phyla are further subdivided into classes, orders, families, genera, and species based on phylogenetic and phenotypic characteristics.

The following is a brief overview of the groups of gram-positive bacteria according to Bergey`s Manual of Systematic Bacteriology (second edition):

Firmicutes (low G+C gram-positive bacteria)

Class Bacilli

The class Bacilli includes aerobic or facultatively anaerobic gram-positive rods and cocci that form endospores or not. They are widely distributed in soil, water, plants, animals, and humans. Some of them are important pathogens (e.g., Bacillus anthracis, Listeria monocytogenes), some are beneficial probiotics (e.g., Lactobacillus, Bifidobacterium), and some are industrially useful (e.g., Bacillus subtilis, Lactococcus lactis).

The class Bacilli is divided into two orders: Bacillales and Lactobacillales. The order Bacillales contains mostly endospore-forming bacteria, such as Bacillus, Clostridium, Paenibacillus, and Staphylococcus. The order Lactobacillales contains mostly non-endospore-forming bacteria that produce lactic acid as a major end product of fermentation, such as Lactobacillus, Streptococcus, Enterococcus, and Leuconostoc.

Class Clostridia

The class Clostridia includes obligately anaerobic gram-positive rods that form endospores. They are found in various habitats, such as soil, sediments, animal intestines, and human infections. Some of them are notorious pathogens (e.g., Clostridium botulinum, Clostridium tetani, Clostridium difficile), some are beneficial symbionts (e.g., Clostridium acetobutylicum), and some are involved in biogeochemical cycles (e.g., Clostridium thermocellum).

The class Clostridia is divided into six orders: Clostridiales, Halanaerobiales, Natranaerobiales, Thermoanaerobacteriales, Thermolithobacteriales, and Symbiobacterales. The order Clostridiales contains the majority of clostridia species that are characterized by their diverse metabolic pathways and substrate utilization. The other orders contain specialized clostridia that inhabit extreme environments or form symbiotic associations with other organisms.

Actinobacteria (high G+C gram-positive bacteria)

Class Actinobacteria

The class Actinobacteria includes aerobic or microaerophilic gram-positive rods or filaments that often form branching hyphae or spores. They are abundant in soil and play important roles in decomposition and bioremediation. Some of them produce antibiotics or other bioactive compounds (e.g., Streptomyces, Actinomadura), some are pathogens or opportunists (e.g., Mycobacterium, Corynebacterium), and some are commensals or symbionts (e.g., Propionibacterium, Frankia).

The class Actinobacteria is divided into five subclasses: Acidimicrobidae, Coriobacteridae, Rubrobacteridae, Sphaerobacteridae, and Actinobacteridae. The subclass Actinobacteridae contains the majority of actinobacteria species that are characterized by their complex morphological differentiation and secondary metabolism. The other subclasses contain less diverse and less studied actinobacteria that have distinct phylogenetic and phenotypic features.

Class Thermoleophilia

The class Thermoleophilia includes thermophilic or thermotolerant gram-positive rods or cocci that are aerobic or facultatively anaerobic. They are found in hot springs, compost, and other high-temperature environments. They are of interest for their potential biotechnological applications and their evolutionary relationships with other bacteria.

The class Thermoleophilia is divided into two orders: Thermoleophilales and Solirubrobacterales. The order Thermoleophilales contains mostly thermophilic bacteria that grow optimally above 50°C, such as Thermoleophilum, Geothermicoccus, and Thermicanus. The order Solirubrobacterales contains mostly thermotolerant bacteria that grow optimally below 50°C, such as Solirubrobacter, Patulibacter, and Conexibacter.

Some bacteria do not have a cell wall at all, but instead have a tough cytoplasmic membrane that protects them from osmotic changes. These bacteria belong to the phylum Tenericutes, which includes the genus Mycoplasma and its relatives . Mycoplasmas are pleomorphic (variable in shape) and very small (0.1-0.2 μm), comparable to some viruses. They are also phylogenetically related to the Firmicutes, a group of mostly gram-positive bacteria with cell walls.

Mycoplasmas are parasitic or saprophytic bacteria that live inside or on the surface of animal cells. They cause various diseases in humans and other animals, such as pneumonia, urethritis, mastitis, and arthritis. They are not affected by antibiotics that target cell wall synthesis, such as penicillin, but they are sensitive to other antibiotics that act on different cellular targets. Mycoplasmas acquire cholesterol from their environment and use it to form sterols in their cytoplasmic membrane, which help to increase its stability and resistance to rupture . Some mycoplasmas also have lipoglycans, which are long-chain heteropolysaccharides attached to membrane lipids. Lipoglycans help to stabilize the membrane and facilitate the attachment of mycoplasmas to host cell receptors.

Another type of bacteria that lack a cell wall are the L-forms, which are derived from normal bacteria that have lost their ability to form a cell wall under certain conditions, such as exposure to antibiotics or nutrient deprivation. L-forms can be formed by both gram-positive and gram-negative bacteria, and they have varied shapes and sizes. They are very sensitive to osmotic shock and can revert back to their normal form when the conditions change. L-forms are not stable like mycoplasmas, and they are not considered a natural group of bacteria.

Protoplasts and spheroplasts are similar to L-forms, but they are artificially created by treating bacteria with enzymes that degrade their cell walls. Protoplasts are derived from gram-positive bacteria and have no cell wall remnants, while spheroplasts are derived from gram-negative bacteria and have some peptidoglycan fragments left in their outer membrane. Both protoplasts and spheroplasts are very fragile and susceptible to osmotic lysis. They can be used for genetic studies or for fusion experiments with other cells.

Some Archaea also lack a cell wall, such as the Thermoplasma group, which live in hot and acidic environments. They have a cytoplasmic membrane composed of tetraether lipids that form a monolayer instead of a bilayer. This makes their membrane more rigid and resistant to heat and pH changes. Thermoplasma species are related to the Euryarchaeota, a group of Archaea that includes methanogens and halophiles.

Archaebacteria, also known as Archaea, are a domain of single-celled prokaryotic organisms that differ from bacteria in many aspects of their biochemistry and genetics. They were initially classified as bacteria and called archaebacteria, but this term is now obsolete. Archaebacteria are found in diverse habitats, including extreme environments such as hot springs, salt lakes, acidic waters, and anaerobic sediments. They play important roles in biogeochemical cycles, such as carbon, nitrogen, and sulfur cycling.

In the ninth edition of Bergey`s Manual of Determinative Bacteriology, archaebacteria are divided into five groups based on their cell wall composition, morphology, and metabolism. These groups are:

• Group 31: Methanogens - These are anaerobic archaebacteria that produce methane as a metabolic by-product. They are found in various habitats, such as swamps, marshes, animal guts, and sewage treatment plants. They use carbon dioxide, acetate, methanol, or methylamines as electron acceptors and hydrogen, formate, or carbon monoxide as electron donors. Some examples of methanogens are Methanobacterium, Methanococcus, Methanosarcina, and Methanopyrus.

• Group 32: Archaeal sulfate reducers - These are anaerobic archaebacteria that reduce sulfate to sulfide as a metabolic by-product. They are found in marine sediments and hydrothermal vents. They use organic compounds or hydrogen as electron donors and sulfate or sulfite as electron acceptors. Some examples of archaeal sulfate reducers are Archaeoglobus and Thermocladium.

• Group 33: Extremely halophiles - These are archaebacteria that require high salt concentrations (usually above 15%) for growth. They are found in salt lakes, salterns, and brines. They use light or organic compounds as energy sources and oxygen or nitrate as electron acceptors. Some examples of extremely halophiles are Halobacterium, Haloarcula, Halococcus, and Natronobacterium.

• Group 34: Cell wall-less archaebacteria - These are archaebacteria that lack a cell wall and have a membrane composed of glycoprotein subunits. They are found in acidic hot springs and solfataras. They use sulfur or hydrogen as electron donors and oxygen or ferric iron as electron acceptors. Some examples of cell wall-less archaebacteria are Thermoplasma and Picrophilus.

• Group 35: Extremely thermophilic and hyperthermophilic sulfur metabolizers - These are archaebacteria that grow optimally at temperatures above 80°C (176°F) and some even above 100°C (212°F). They are found in geothermal areas such as hot springs and hydrothermal vents. They use sulfur or hydrogen as electron donors and oxygen or sulfur compounds as electron acceptors. Some examples of extremely thermophilic and hyperthermophilic sulfur metabolizers are Sulfolobus, Thermoproteus, Pyrodictium, and Pyrococcus.

These five groups of archaebacteria represent the diversity and uniqueness of this domain of life. They have many features that distinguish them from bacteria and eukaryotes, such as their ether-linked lipids, their unusual ribosomal RNA sequences, their distinctive transcription and translation machinery, and their novel metabolic pathways. Archaebacteria are fascinating organisms that deserve more attention and research.

Bergey’s manual of systematic bacteriology is a comprehensive reference work that covers the diversity, taxonomy, and ecology of bacteria. It is based on phylogenetic analysis of molecular data, such as ribosomal RNA sequences, as well as phenotypic and biochemical characteristics. The manual aims to provide a natural classification of bacteria that reflects their evolutionary history and relationships.

The manual consists of four volumes, each covering a major group of bacteria. The first volume, published in 1984, deals with the archaea and the deeply branching and phototrophic bacteria. These are the most ancient and primitive forms of life on Earth, and they include some extremophiles that can survive in harsh environments. The second volume, published in 1986, covers the proteobacteria, which are the largest and most diverse group of gram-negative bacteria. They include many medically and environmentally important genera, such as Escherichia, Salmonella, Vibrio, Pseudomonas, and Rhizobium. The third volume, published in 1989, focuses on the low G+C gram-positive bacteria, which have a low ratio of guanine and cytosine nucleotides in their DNA. They include many common and beneficial bacteria, such as Bacillus, Lactobacillus, Streptococcus, and Staphylococcus. The fourth volume, published in 1991, covers the high G+C gram-positive bacteria and the actinobacteria. These are bacteria that have a high ratio of guanine and cytosine nucleotides in their DNA, and they include many soil-dwelling and filamentous forms, such as Mycobacterium, Corynebacterium, Nocardia, and Streptomyces.

Each volume of the manual contains detailed descriptions of the genera and species within each group of bacteria, as well as information on their morphology, physiology, metabolism, ecology, pathogenicity, and biotechnology. The manual also provides keys and tables for identification of bacteria based on various criteria. The manual is intended for microbiologists, biologists, medical professionals, environmental scientists, and anyone interested in the study of bacteria.

The manual is currently undergoing a revision for its third edition, which will be published in electronic format. The third edition will reflect the latest advances in bacterial taxonomy and phylogeny, as well as incorporate new data from genomics and metagenomics. The third edition will also include more illustrations and photographs to enhance the visual presentation of bacterial diversity. The third edition is expected to be completed by 2024.

Bergey`s manuals are widely used and respected sources of information on bacterial taxonomy and identification. They have several advantages, such as:

• They provide comprehensive and updated information on the diversity, morphology, physiology, ecology, and phylogeny of bacteria.
• They are based on extensive research and expert opinions from various fields of microbiology.
• They are organized in a logical and consistent manner, using a hierarchical system of classification that reflects the evolutionary relationships among bacteria.
• They offer practical guidance and tools for identifying bacteria in the laboratory, such as keys, tables, diagrams, and descriptions.
• They include references to the original literature and other sources of information for further study.

However, Bergey`s manuals also have some limitations, such as:

• They are not always consistent with each other or with other sources of bacterial classification, especially when new discoveries or revisions are made.
• They are not comprehensive enough to cover all the known bacterial species and genera, let alone the unknown ones.
• They are not always accurate or reliable, as some information may be outdated, incomplete, or erroneous.
• They are not easy to access or use, as they are expensive, bulky, and require specialized knowledge and skills.

Therefore, Bergey`s manuals should be used with caution and critical thinking, and supplemented with other sources of information when necessary. They should also be updated regularly to reflect the advances and changes in bacterial taxonomy and identification.

We are Compiling this Section. Thanks for your understanding.