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The Deinococci, Mollicutes, and Nonproteobacterial Gram-Negative Bacteria 1 21 Copyright © McGraw-Hill Global Education Holdings, LLC. Permission required.

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Presentation on theme: "The Deinococci, Mollicutes, and Nonproteobacterial Gram-Negative Bacteria 1 21 Copyright © McGraw-Hill Global Education Holdings, LLC. Permission required."— Presentation transcript:

1 The Deinococci, Mollicutes, and Nonproteobacterial Gram-Negative Bacteria 1 21 Copyright © McGraw-Hill Global Education Holdings, LLC. Permission required for reproduction or display.

2 Deinococcus Extraordinarily resistant to desiccation and radiation –can survive 3–5 million rad (100 rad lethal to humans) Isolated from ground meat, feces, air, fresh water, and other sources, but natural habitat unknown 2

3 Deinococcus Genome consists of two circular chromosomes, a megaplasmid, and a small plasmid –radiation resistance due to ability to repair genome when it is severely damaged –efficient proteins (protected by manganese) and enzymes for DNA repair Within 12–24 hours can repair chromosomes fragmented by exposure to radiation 3

4 4 The Mycoplasmas Lack cell walls and are pleomorphic –cannot synthesize peptidoglycan precursors –sterols may stabilize plasma membrane –smallest bacteria capable of self-reproduction –grow as fried egg appearance on agar surface

5 5 More about The Mycoplasmas Genomes –less than 1000 genes –one of the smallest found in prokaryotes

6 6 Important Pathogens Mycoplasma mycoides – pleuropneumonia in cattle Mycoplasma gallisepticum – chronic respiratory disease in chickens Mycoplasma hyopneumoniae – swine pneumonia Mycoplasma pneumoniae – primary atypical pneumonia in humans Ureaplasma urealyticum – premature birth, neonatal meningitis and pneumonia spiroplasmas – pathogenic in insects, ticks, and a variety of plants

7 The Photosynthetic Bacteria: 5 Groups Cyanobacteria – oxygenic photosynthetic bacteria Anoxygenic phototrophic bacteria:(These range from photolithoautotrophs to photoorganoheterotrophs) –Purple bacteria –Purple non-sulfur bacteria –Green non-sulfur bacteria –Green sulfur bacteria 7

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9 Photosynthetic Bacteria The cyanobacteria –carry out oxygenic photosynthesis use water as an electron donor and generate oxygen during photosynthesis The purple and green bacteria carry out anoxygenic photosynthesis and use a variety of organic and inorganic nutrients for electron donors (lithotrophs or organotrophs) and carbon (autotrophs or heterotrophs) 9

10 Photosynthetic Microbes Differences in photosynthetic pigments, with distinct absorption spectra, and oxygen requirements are important ecologically –inhabit different layers of water environments 10

11 The Cyanobacteria Largest, most diverse group of photosynthetic bacteria –Chlorophyceae – “blue green algae” common term Many are obligate photolithoautotrophs; some can grow slowly in dark as chemoheterotrophs Important in nitrogen cycle (provide fertilizer for cultivation of rice and bean crops) Fossil records date back 3.8 million years Responsible for the Earth’s atmosphere Endosymbiosis leading to eukaryotic plants Have chlorophyll a 11

12 More about Cyanobacteria Some storage structures have –carboxysomes (enzymes for Calvin cycle) –cyanophycin Range in diameter from ~1 to 10  m May be unicellular, colonial, or filaments 12

13 More about Cyanobacteria Pigmentation –most appear blue-green due to presence of phycocyanin –presence of phycoerythrin in many ocean isolates gives them red or brown coloration –chromatic adaption modulation of pigment concentrations in different light Phototaxis by use of gas vacuoles 13

14 Specialized Reproductive Cells and Structures Binary fission, budding, fragmentation, multiple fission Hormogonia –small, motile fragments of filamentous cyanobacteria Akinetes –dormant, thick-walled resting cells resistant to desiccation –often germinate to form new filaments Baeocytes –produced by multiple fission –small spherical cells; escape when outer wall ruptures –some are motile by gliding motility 14

15 Heterocysts Specialized cells used for nitrogen fixation –produced when organism is nitrogen deprived –differentiate from individual cells in filament –thick heterocyst wall prevents O 2 diffusion into heterocyst which would inactivate nitrogenase 15

16 Ecology of Cyanobacteria - 1 Tolerant of environmental extremes –thermophilic species can grow at temperatures up to 75°C –often are primary colonizers Can cause blooms in nutrient-rich ponds and lakes –some produce toxins 16

17 Ecology of Cyanobacteria - 2 Often form symbiotic relationships –e.g., are phototrophic partner in most lichens –e.g., symbionts with protozoa and fungi –e.g., nitrogen-fixing species form plant associations Profound effect on global carbon cycle Synechococcus, Prochlorococcus –two marine genera; ~1/3 of global CO 2 fixation –less than 1% of ocean mass 17

18 The Chlamydia Obligate intracellular parasites –must grow and reproduce inside host cells –although known for ability to cause disease, many grow within hosts such as protists, and animal cells without adverse effects One class, one order, four families, six genera –genus Chlamydia is best studied 18

19 Genus Chlamydia Nonmotile, coccoid, Gram-negative –cell walls lack muramic acid in peptidoglycan –have very small genomes Obligate intracellular parasites with unique developmental cycle –elementary body (EB) attaches to host cell –reticulate body (RB) reproduction by binary fission –differentiate back into EB, lyses cell 19

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21 Chlamydial Metabolism Cannot catabolize carbohydrates Cannot synthesize ATP or NAD + –import up from host –do have genes for substrate-level phosphorylation, electron transport, and oxidative phosphorylation RBs have biosynthetic capabilities when supplied precursors from host; can synthesize some amino acids EBs seem to be dormant forms 21

22 Chlamydial diseases Chlamydia is the most frequently reported sexually transmitted bacterial disease –1.3 million cases in US in 2010 –number underestimated due to asymptomatic cases –Chlamydia trachomatis is the most commonly isolated species –transmitted through anal, oral, and vaginal sex; can also be transmitted from mother to child during delivery 22

23 Chlamydial diseases Clinical manifestations –in males asymptomatic or urethral discharge, and itching and inflammation of genital tract –in females sometimes asymptomatic may cause PID if pregnant, can lead to miscarriage, stillbirth, inclusion conjunctivitis, and infant pneumonia 23

24 Trachoma Caused by C. trachomatis serotypes A-C Transmitted by hand-to-hand contact, contact with infected soaps and towels, and flies, also mother–child contact in adults The greatest single cause of blindness throughout the world 24

25 Trachoma Clinical manifestations –first infection abrupt onset of inflamed conjunctiva, leading to inflammatory cell exudate and necrotic eyelash follicles usually heals spontaneously –reinfection pannus formation (vascularization of cornea), leading to scarring of conjunctiva if scarring of cornea also occurs, blindness results 25

26 Psittacosis (Ornithosis) Caused by Chlamydophilia psittaci (previously Chlamydia psittaci) –enters respiratory tract, transported to and reproduces in liver and spleen, and then invades lungs Infectious disease of birds –transmitted to humans by direct contact with infected birds or by inhalation of dried bird excreta –occupational hazard in poultry industry 26

27 Psittacosis Clinical manifestations –inflammation and hemorrhaging of lung tissue and pneumonia Diagnosis –isolation from blood or sputum, or by serology Treatment, prevention, and control –antibiotic therapy –chemoprophylaxis for pet birds and poultry 27

28 Chlamydial Pneumonia Caused by Chlamydia pneumoniae –obligate intracellular parasite –may also play role in coronary artery disease and vascular disease at other sites Transmission probably human to human by respiratory secretions –elementary bodies infect, reticular bodies replicate 28

29 Chlamydial Pneumonia Clinical manifestations –fever, productive cough, and mild pharyngitis, bronchitis, and sinusitis Diagnosis, treatment, prevention –observation of symptoms and a microimmunofluorescence test –antibiotic therapy 29

30 The Spirochaetes Contains one class; one order, three families, 13 genera Gram-negative, chemoheterotrophic bacteria with distinctive structure and motility –slender, long with flexible helical shape –creeping (crawling) motility due to a structure called an axial filament Oxygen requirements vary 30

31 Symbiotic Associations between Spirochetes and Other Organisms Ecologically diverse –free living –symbiotic hindguts of termites digestive tracts of mollusks and mammals oral cavities of animals –disease Lyme disease, syphilis and leptospirosis are spirochete diseases 31

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33 Syphilis Caused by Treponema pallidum subsp. pallidum Venereal syphilis – sexually transmitted Congenital syphilis – acquired in utero 33

34 Syphilis Diagnosis –clinical history, microscopic examination, and serology Treatment, prevention, and control –antibiotic therapy most effective in early stages –public education, prompt treatment of new cases, follow-up on sources and contacts, sexual hygiene, and use of condoms 34

35 Lyme Disease LD or Lyme borreliosis Most common tick-borne disease in the U.S. Caused by Borrelia burgdorferi (most common in U.S.), B. garinii, and B. afzelii (most common in Europe and Asia) 35

36 Lyme Disease Transmitted from animal reservoirs by ticks (Ixodes scapularis and I. pacificus) –deer, field mice, and woodrats Complex disease –clinical manifestations vary with three stages of disease –initial, disseminated, late stage 36

37 Stages of Lyme Disease Localized stage –develops 1 week to 10 days after infection –expanding, ring-shaped, skin lesion –flu-like symptoms Disseminated stage –occurs weeks or months after infection –neurological abnormalities, heart inflammation, and arthritis Lyme arthritis may be autoimmune to joint MHC which are similar to bacterial antigens 37

38 Stages of Lyme Disease Late stage –occurs years later –demyelination of neurons, behavioral changes, and symptoms resembling Alzheimer’s disease and multiple sclerosis 38

39 Lyme Disease Diagnosis –serogical testing (Lyme ELISA or Western blot) –isolation of spirochete from patient –detection of Borrelia DNA (PCR) Treatment, prevention, and control –antibiotic therapy most effective in early stages –tick control and avoiding ticks 39

40 Bacteroides Anaerobic, Gram-negative rods, various shapes Often found in oral cavity and intestinal tract of humans and other animals and the rumen of ruminants –often benefit host by degrading complex carbohydrates, providing extra nutrition to host –constitute up to 30% of bacteria from human feces –some cause disease Most common nosocomial anaerobic infection with a 20% fatality rate 40

41 Gliding Motility - 1 Characteristic of the Bacteriodetes Also present in many other taxa –fruiting and nonfruiting aerobic chemoheterotrophs –cyanobacteria –green nonsulfur bacteria –at least two Gram-positive genera 41

42 Gliding Motility - 2 Gliding mechanism unknown –occurs when cells in contact with solid surface –cells leave slime trail; motility often lost with age –low-nutrient levels usually stimulate gliding 42

43 Advantages of Gliding Motility Enables cells to encounter insoluble nutrient sources and digest them with cell bound digestive enzymes Works well in drier habitats (e.g., soil, sediments, and rotting wood) Enables cells to position themselves optimally for light intensity, [O 2 ], [H 2 S], temperature, etc. 43


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