Major groups of bacteria: Spirochetes, Chlamydia, Rickettsia, nanobes, mycoplasma, VBNC, myxobacteria, archaebacteria.

Manor groups of bacteria

1. Major groups of bacteria Submitted to: DR. AKHIL SOORYA SUBMITTED BY: AISWARYA s NAIR DEPARTMENT OF BOTANY 1 st YEAR M.SC BOTANY

2. SPIROCHETES

3. They are gram-negative, motile, spiral bacteria, 10 to 30 µm long and diameters around 0.1–0.6 µm. T hey are unique in having endo cellular flagella  called axial fibrils/axial filaments, which run lengthwise between the bacterial inner membrane and outer membrane in periplasmic space. They number between 2 & more than100 per organism, depending upon the species.

4. E ach axial fibril attaches at an opposite end and winds around the cell body, which is enclosed by an envelope.

5. Reproduce by undergoing asexual transverse binary fission. They are micro-aerophilic or anaerobic and are extremely sensitive to oxygen toxicity. S ome of them are serious pathogens for humans, causing diseases such as syphilis, yaws, lyme diseases & relapsing fever .  T he order of spirochaetales is divided into two families: 1. Spirochaetaceae 2. Leptospiraceae

6. Examples of genera of spirochetes include   S pirochaeta ,  T reponema ,  B orrelia , and   L eptospira . Treponema   includes the agents of syphilis ( T. Pallidum pallidum ) and yaws (T. Pallidum pertenue ). Borrelia i ncludes several species transmitted by lice & ticks and causing relapsing fever ( B. Recurrentis  and others) and lyme disease (B. Burgdorferi ) in humans.   Spirochaeta  are free-living non pathogenic inhabitants of mud and water, typically thriving in anaerobic (oxygen-deprived) environments. Leptospirosis, caused by  Leptospira , is principally a disease of domestic and wild mammals and is a secondary infection of humans.

7. RICKETTSIA Rickettsia  is a genus of non motile, gram-negative, non spore forming, highly pleomorphic bacteria. Occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "rickettsia" has nothing to do with Rickets (which is a deficiency disease  resulting from lack of vitamin D); . T he bacterial genus  rickettsia   instead was named after Howard Taylor Ricketts , in honor of his pioneering work on tick-borne spotted fever.

8. Being obligate intracellular bacteria, rickettsias depend on entry, growth, and replication within the cytoplasm of living eukaryotic host cells (typically endothelial cells). Rickettsia  species cannot grow in artificial nutrient culture; they must be grown either in tissue or embryo cultures; typically, chicken embryos are used. They include the genera rickettsiae, ehrlichia, orientia, and coxiella . These zoonotic pathogens cause infections that disseminate in the blood to many organs.

9. Many new strains or species of  rickettsia  are described each year. S ome are pathogens of medical and veterinary interest, but many are non-pathogenic to vertebrates, including humans, and infect only arthropods, often non-hematophagous, such as aphids or whiteflies. Many species are thus arthropod-specific symbionts. Pathogenic  rickettsia  species are transmitted by numerous types of arthropods, including chiggers, ticks, fleas, mites, mammals & lice. They are associated with both human and plant diseases. R ickettsia  species are the pathogens responsible for typhus, rickettsialpox boutonneuse fever, African tick bite fever, rocky mountain spotted fever, flinders island spotted fever.

10. The classification of  rickettsia  into three groups spotted fever, typhus, and scrub typhus was initially based on serology. This grouping has since been confirmed by DNA sequencing. All three of these groups include human pathogens. Rickettsias are more widespread than previously believed and are known to be associated with arthropods, leeches, & protists. Arthropod-inhabiting rickettsiae are generally associated with reproductive manipulation (such as parthenogenesis) to persist in host lineage.

11. CHLAMYDIA Chlamydia are obligatory intacellular bacteria and together with Rickettsia occupy a unique niche in the microbiology world. For a long time, chlamydia were classified as viruses because of their dependence on the host cell. Since the chlamydia contain RNA, DNA & ribosomes, a double cell wall, and are suscepctible to antibiotics, they were later classified as bacteria. At present, the genus chlamydia comprises three species. These are Chlamydia trachomatis , Chlamydia pneumoniae and Chlaymidia psittaci .

12. MYCOPLASMAS The mycoplasmas are essentially bacteria lacking a rigid cell wall during their entire life cycle, although they are also much smaller than bacteria. The first organism of this type was associated with pleuropneumonia of cattle, and was originally called the pleuropneumonia like organism (PPLO). Systemic position •DOMAIN: BACTERIA •PHYLUM: TENERICUTES •CLASS: MOLLICUTES •ORDER: MYCOPLA SMATALES •FAMILY: MYCOPLASMATACEAE •GENUS: MYCOPLASMa

13. STRUCTURE OF MYCOPLASMA

14. Nocard and Roux contributed for mycoplasma discovery • IN 1896 NOCARD AND RAUX REPORTED THAT CULTIVATION OF THE CAUSATIVE AGENT OF CONTAGIOUS BOVINE PLEUROPNEUMONIA {CBPP}, WHICH WAS AT THAT TIME A GRAVE AND WIDESPREAD DISEASE IN CATTLE HERDS. THE WORK OF NOCARD AND ROUX REPRESENTED THE FIRST ISOLATION OF A MYCOPLASMA SPECIES. HISTORY OF MYCOPLASMA • THE NAME MYCOPLASMA FROM THE GREEK MYKES(FUNGAS) AND PLASMA(FORMED),WAS PROPOSED IN THE 1950s,REPLACING THE TERM PLEURO PNEUMONIA-LIKE ORGANISMS (PPLO).REFERRING TO ORGANISMS SIMILAR TO THE CAUSTIVE AGENT OF CBPP.IT WAS LATER FOUND THAT THE FUNGUS-LIKEGROWTH PATTERN OF M.MYCOIDES IS UNIQUE TO THAT SPECIES Nocard and Roux contributed for mycoplasma discovery . • In 1896 Nocard and Roux reported that cultivation of the causative agent of Contagious Bovine Pleuro Pneumonia {CBPP}, which was at that time a grave and widespread disease in cattle herds. The work of Nocard and Roux represented the first isolation of a mycoplasma species. • The name mycoplasma from the Greek mykes (fungus) and plasma (formed),was proposed in the 1950s, replacing the term Pleuro Pneumonia-Like Organisms (PPLO).

15. Prokaryotic, without rigid cell wall. Have no flagella, produce no spores & are gram negative. Mycoplasma species are among the smallest organisms yet discovered. Bounded by triple-layered membrane. Peptidoglycan is absent. This makes them naturally resistant to antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. They can survive without oxygen. Several species are pathogenic in humans, including M. pneumoniae , which is an important cause of walking pneumonia and other respiratory disorders. M.genitalium , which is believed to be involved pelvic inflammatory diseases.

16. Their cells can be conformed to different shape. Eg: M. genitalium - Flask shaped, M.pneumoniae – More elongated. Many other species are coccoid. These shapes contribute to the ability of mycoplasmas to thrive in respective environments. Eg : M. pneumoniae ; cells possess an extended ‘arm’ protruding from a coccoid cell body, which is involved in the attachment of this pathogenic bacterium to the tissue of human host, in movement along solid surfaces, and in cell division. Mycoplasma species are often found in research laboratories as contaminants in cell culture. Mycoplasma cells are physically small (<1µm), so are difficult to detect with a conventional microscope. Detection techniques include DNA probe/enzyme immuno assay/PCR/sensitive agar & staining with DNA stain.

17. They are normally destroyed by heat at 45°c in 15 minutes. They are relatively resistant to Pencillins, and Cephalosporins. Sensitive to tetracyclines, and several other antibiotics. They usually reproduce by binary fission budding or round body formation and filamentous formation . Scientists have isolated at least 17 species of mycoplasma from humans, 4 types of organisms are responsible for most clinically significant infections. These species are Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma species.

18. MYCOPLASMA PNEUMONIAE UREAPLASMA SPECIES

19. MYCOPLASMA HOMINIS MYCOPLASMA GENITALIUM

20. NANOBES

21. A new controversy discovery by scientists as tiny cells that look like dwarf bacteria but are ten times smaller than mycoplasma and hundred times smaller than the average bacterial cell. Nanobacteria like forms were first isolated from blood & serum samples. N a nobacteria are thought to have been found in human blood and may be related to health issues such as formation of kidney stones due to their biomineralization processes.

22. VBNC s Viable but non-culturable cells (VBNC) are defined as live bacteria, but which do not either grow or divide. They cannot be cultivated on conventional media. They do not form colonies on solid media and do not change broth appearance. Many bacterial species have been found to exist in a viable but non-culturable (VBNC) state since its discovery in 1982.

23.   It was first discovered in 1982 that  E scherichia coli  and  V ibrio cholerae  cells could enter a distinct state called the viable but non-culturable (VBNC) state. Unlike normal cells that are culturable on suitable media and develop into colonies, VBNC cells are living cells that have lost the ability to grow on routine agar media, on which they normally grow which impairs their detection by conventional plate count techniques. This leads to an underestimation of total viable cells in environmental or clinical samples, and thus poses a risk to public health.

24. Despite their non-culturability on normally permissive media, VBNC cells are not regarded as dead cells. Because VBNC cells have an intact membrane containing undamaged genetic information. The plasmids, if any, are also retained in VBNC cells. While dead cells are metabolically inactive, VBNC cells are metabolically active and carry out respiration. High ATP level was found in  L isteria monocytogenes  even one year after entering the VBNC state. Moreover, dead cells do not express genes, while VBNC cells continue transcription and therefore, mRNA production. In contrast to dead cells that no longer utilize nutrients, VBNC cells were shown to have continued uptake and incorporation of amino acids into proteins .

25. Viable but non-culturable stage is reversible. Both gram positive and gram negative bacteria can enter the VBNC stage. Many studies show that processes meant to achieve bactericidal effects can favour bacterial switch to VBNC. The switch to this stage shown by several bacteria species; Vibrio species ( cholerae, vulnificus, Escherichia coli ), Salmonella spp. , Pseudomonas spp. ( Mycobacterium tuberculosis), Enterococcus spp. etc.

26. MYXOBACTERIA

27. Myxobacteria "slime bacteria“ are a group of bacteria that predominantly live in the soil and feed on insoluble organic substances. Have very large genomes relative to other bacteria One species of myxobacteria, Minicystis rosea , has the largest known bacterial genome with over 16 million nucleotides. The second largest is another myxobacteria Sorangium cellulosum . Move by gliding. They typically travel in swarms (also known as wolf packs), containing many cells kept together by intercellular molecular signals. Myxobacteria are used to study the polysaccharide production in gram-negative bacteria like the model Myxococcus xanthus .

28. Myxococcus xanthus Myxobacteria are also good models to study the multicellularity in the bacterial world.

29. ( A) M yxococcus xanthus - fruiting bodies emerging from a soil particle. (B) sketch of a C hondromyces crocatus fruiting body. (C) spherical spore and vegetative rod forms of M. xanthus cells. Myxobacterial social phenotypes .

30. (D ) Sketch of a C hondromyces aurantiacus - fruiting body. (E) M. Xanthus - fruiting body. (F) Sketch of a M yxococcus coralloides fruiting body. (G) M. Xanthus cells engaging in coordinated motility. (H) Sketch of swarming and individual cells of C. a urantiacus. (I) M. Xanthus swarm (movement left to right) consuming a colony of E scherichia coli.

31. Natural products from myxobacteria: novel metabolites and bioactivities Myxobacteria produce a number of biomedically and industrially useful chemicals, such as antibiotics, and export those chemicals outside the cell. Myxobacteria are a rich source for structurally diverse secondary metabolites with intriguing biological activities. New natural products were isolated from myxobacteria in the period of 2011 to 2016.

32. archaebacteria Archaebacteria are known to be the oldest living organisms on earth. They belong to the kingdom Monera and are classified as bacteria because they resemble bacteria when observed under a microscope. Apart from this, they are completely distinct from prokaryotes. However, they share slightly common characteristics with the eukaryotes.

33. Archaebacteria are obligate or facultative anaerobes, ie, They flourish in the absence Of oxygen and that is why only they can undergo methanogenesis. The cell membranes of the archaebacteria are composed of lipids. The rigid cell wall provides shape and support to the archaebacteria. It also protects the cell from bursting under hypotonic conditions. The cell wall is composed of pseudomurein , which prevents archaebacteria from the effects of lysozyme. Lysozyme is an enzyme released by the immune system of the host, which dissolves the cell wall of pathogenic bacteria.

34. They do not possess membrane-bound organelles such as nuclei, endoplasmic reticulum, mitochondria, lysosomes or chloroplast. Its thick cytoplasm contains all the compounds required for nutrition and metabolism. They can live in a variety of environments and are hence called extremophiles. They can survive in acidic and alkaline aquatic regions, and also in temperature above Boiling point. They can withstand a very high pressure of more than 200 atmospheres. Archaebacteria are indifferent towards major antibiotics because they contain Plasmids which have antibiotic resistance enzymes.

35. The mode of reproduction is asexual, known as binary fission. They perform unique gene transcription. The differences in their ribosomal RNA suggest that they diverged from both prokaryotes and eukaryotes. Types of Archaebacteria : There are the 3 types of archaebacteria. A rchaea that live in salty environments are known as halophiles . Archaea that live in extremely hot environments are called thermoacidophiles . Archaea that produce methane are called methanogens . Archaebacteria are classified on the basis of their phylogenetic relationship. The major types of archaebacteria are : Crenarchaeota, Euryarchaeota, Korarchaeota, Thaumarchaeota & Nanoarchaeota.

36. Examples of Archaebacteria : Lokiarcheota It is a thermophilic archaebacterium found in deep-sea vents known as the Loki’s castle. It has a unique genome. Some of the genes of the genome are involved in phagocytosis. They also possess the eukaryotic genes that are used by the eukaryotes to control their shapes. It is believed that Lokiarcheota and eukaryotes shared a common ancestor several billion years ago.

37. Methanobrevibacter smithii It is a methane-producing bacteria found in the human gut. It helps in the breakdown of complex plant sugars and extracts energy from the food consumed by us. Some help to protect against colon cancer. People suffering from colon cancer and obesity have very high levels of euryarchaeota bacteria in their gut.

38. ACTINOMYCETES Actinomycetes are  a group of unicellular filamentous bacteria that form a branching network of filaments and produce spores . They have long been recognized as sources of severe earthy-musty tastes and odours in drinking water. Gram stain:  Gram positive Morphology:  Filamentous lengths of cocci Respiration:  Mostly aerobic, can be anaerobic Habitat:  Soil or marine.

39. Actinomycetes are a broad group of bacteria that form thread-like filaments in the soil. The distinctive scent of freshly exposed, moist soil is attributed to these organisms, especially to the nutrients they release as a result of their metabolic processes. Actinomycetes form associations with some non-leguminous plants and fix N, which is then available to both the host and other plants in the near vicinity.

40. The  actinomycetota  (or  actinobacteria ) are a phylum of mostly gram positive bacteria . They can be terrestrial or aquatic.  They are of great economic importance to humans because agriculture and forests depend on their contributions to soil systems. In soil they help to decompose the organic matter of dead organisms so the molecules can be taken up anew by  plants . A ctinomycetota  is one of the dominant bacterial phyla under actinomycetes and contains one of the largest of bacterial genera,  streptomyces. S treptomyces  and other actinomycetota are major contributors to biological buffering of soils. T hey are also the source of many antibiotics. 

41. Actinomycetota , especially  streptomyces  spp., are recognized as the producers of many bioactive metabolites that are useful to humans in: M edicine such as antibacterials, antifungals, antivirals, antithrombotics, immunomodifiers, antitumor drugs, E nzyme inhibitors, in agriculture, including insecticides, herbicides, fungicides, & growth-promoting substances for plants and animals. A ctinomycetota -derived antibiotics that are important in medicine include aminoglycosides, anthracyclines, chloramphenicol, macrolide, tetracyclines etc. Actinomycetota  have high guanine a nd cytosine content in their DNA.

42. Actinomycetes are soil microorganisms like both bacteria and fungi, & have characteristics linking them to both groups. They have many processes that are beneficial to soil health including: Decomposition of cellulose matter Ammonium fixation and synthesis Degradation of humus Disease resistance Act as biocontrol agents Bioremediation of lignin, cellulose, petroleum, and heavy metal contaminants

43. They play major roles in the cycling of organic matter; inhibit the growth of several plant pathogens in the rhizosphere and decompose complex mixtures of polymer in dead plant, animal and fungal material results in production of many extracellular enzymes which are conductive to crop production. The major contribution in biological buffering of soils, biological control of soil environments by nitrogen fixation and degradation of high molecular weight compounds like hydrocarbons in the polluted soils are remarkable characteristics of actinomycetes. Besides this, they are known to improve the availability of nutrients, minerals, enhance the production of metabolites and promote plant growth regulators.

44. SUBMITTED BY : AISWARYA S NAIR 1 ST MSC BOTANY THANK YOU