1. 21
The Deinococci, Mollicutes, and Nonproteobacterial Gram-Negative Bacteria
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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

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

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

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

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)

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

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

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

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

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

15. Heterocysts Specialized cells used for nitrogen fixation
produced when organism is nitrogen deprived
differentiate from individual cells in filament
thick heterocyst wall prevents O2 diffusion into heterocyst which would inactivate nitrogenase

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

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 CO2 fixation
less than 1% of ocean mass

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

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

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

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

23. Chlamydial diseases Clinical manifestations in males in females
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
Chlamydial diseases

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

25. Trachoma Clinical manifestations first infection reinfection
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

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

27. Psittacosis Clinical manifestations Diagnosis
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

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

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

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

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

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

34. Syphilis Diagnosis Treatment, prevention, and control
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

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)
Borrelia burgdorferi

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

37. Stages of Lyme Disease Localized stage Disseminated 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

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

39. Lyme Disease Diagnosis Treatment, prevention, and control
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

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

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

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

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, [O2], [H2S], temperature, etc.