Unit 2 (Chapters 11, 12)

five groups of atypical bacteria

1) fungus-like bacteria
2) acid-fast bacteria
3) mycoplasmas
4) chlamydias
5) rickettsias

fungus-like bacteria

• gram-positive bacilli
• branching filaments like mold
• can form fungus-style reproductive spores
• prokaryotic

examples of fungus-like bacteria

Streptomyces spp. and Actinomyces spp.

why aren't fungus-like bacteria classified as fungi?

• no organelles
• reproduces via binary fission
• susceptible to penicillin (antibiotic) rather than antifungals

which fungi-like bacteria can survive without oxygen?

Actinomyces spp.

spores of fungi-like bacteria

• Streptomyces: conidiospores (asexual)
• Actinomyces: sporangiospores (asexual)

which fungal-like bacteria is used for antibiotics?

Streptomyces spp.

natural habitats of fungal-like bacteria

• Streptomyces: soil
• Actinomyces: normal flora in mouth and throat

which fungal-like bacteria has sulfur granules in pus?

Actinomyces

acid-fast bacteria

• gram-positive bacilli with WAX COAT that retains staining
• cell wall similar to gram-negative cell wall BUT no LPS and has mycolic acid instead (peptidoglycan still present)
• waxy, water-resistant coat to increase survival in environment
• all need oxygen

acid-fast stain chemicals

1) primary: carbolfuchsin
2) mordant: heat (to encourage penetration and retention of dye) or detergent with primary stain (cold method we used)
3) decolonization: acid alcohol (1% HCl in 95% ethanol)
4) methylene blue

natural habitat of acid-fast bacteria

• Nocardia: soil or lungs
• M. tuberculosis: phagocytes/white blood cells
• M. leprae: peripheral nervous system
• M. ulcerans: skin and subcutaneous fat cells

do Mycobacterium release endospores?

no

which acid-fast bacteria forms filaments like fungi?

Nocardia

which acid-fast bacteria is an obligate intracellular parasite?

M. leprae so it cannot grow on artificial media

growth properties of Mycobacterium

• very slow growth rate
• nutrients enter slowly
• dry flaky colonies

how does carbolfuchsin work in acid-fast stain

carbolfuchsin is more soluble in mycolic acid so it retains primary stain more while non-acid-fast bacteria decolorize

mycoplasmas

• smallest (often mistaken as virus) and can pass through filters
• only prokaryotes without a cell wall (stains Gram-negative)
• has sterols in cytoplasmic membrane (similar to eukaryotes)
• pleomorphic due to no cell wall
• fungi-like filaments

which atypical bacteria forms "fried egg" colonies?

mycoplasmas

degenerative evolution

Also called reductive evolution. The loss or mutation of DNA encoding traits that are not under any selection pressure.

which atypical bacteria is undergoing degenerative evolution?

mycoplasmas

Why are mycoplasmas not considered true bacteria?

no cell wall, no organelles, no nucleus

main pathogen of the mycoplasmas

M. pneumoniae

M. pneumoniae disease

• atypical pneumonia (walking pneumonia)
• common in young adults and children
• 20% of pneumonia cases and can be severe
• small colonies under microscope

Ureaplasma (part of mycoplasma)

• enzymatically splits urea in urine
• causes urethritis but is asymptomatic

chlamydias

• submicroscopic
• has cell wall but no peptidoglycan
• gram-negative coccoid
• obligate intracellular parasites and are energy parasites
• spread to humans via interpersonal contact or by airborne routes

two forms of chylamydia cells

elementary body and reticulate body (intermediate body is in between these two forms)

elementary body

• infectious
• rigid cell wall to help it survive outside host
• small

reticulate body

• growth
• fragile cell wall since it doesn't have to survive outside host cell
• large

which chlamydia species can cause blindness amongst other diseases?

Chlamydia trachomatis

which chlamydia species is present in over 50% of the U.S. population?

Chlamydophila pneumoniae (especially in young adults)

rickettsias

• gram-negative rod-shaped or coccobacilli
• obligate intracellular parasites (mammalian cells only)
• slime layer
• anthropod vectors (mostly via insect bites and ticks)
• induce phagocytosis after attachment to enter host

diseases from rickettsias

spotted fever group (spotted fevers and typhus) that damage blood capillary permeability, leading to spotted rash

Rocky Mountain spotted fever

• pathogen: R. richettsii
• vector: ticks

epidemic typhus

• pathogen: R. prowazekii
• vector: lice

endemic murine typhus

• pathogen: R. typhi
• vector: rat fleas

Gram stains of atypical bacteria

positive: fungus-like and acid-fast
negative: mycoplasmas, chlamydias, rickettsias

morphology of atypical bacteria

bacilli: fungus-like and acid-fast
coccoid: chlamydias
coccobacilli: rickettsias
pleomorphic (due to no cell wall): mycoplasmas

cell walls of atypical bacteria

• acid-fast: no LPS, have mycolic acid
• mycoplasmas: no cell wall
• chlamydias: cell wall but no peptidoglycan

which bacteria are obligate intracellular parasites?

chlamydias and rickettsias

which bacteria is the smallest?

mycoplasmas

which bacteria has sterols in the cell membrane?

mycoplasmas

which bacteria have filaments?

fungus-like, mycoplasmas

which bacteria grows on artificial media?

mycoplasmas

which bacteria is known for a slime layer?

rickettsias

archaea cell wall composition

cell walls have no peptidoglycan

are there any known pathogen under the Archaea domain?

no

archaea gram stain

some are gram positive, some are negative based on cell wall composition

different types of extremophiles

• halophiles: high salt
• thermophiles: high temperature
• acidophiles: low pH

methanogens

• Archaea that release methane, a greenhouse gas using inorganic molecules (H2 and CO2)
• can be used for sewage-treatment processes
• part of normal flora
• strictly anaerobic
• very small and can pass through cell filter

Pyrodictium abyssi

member of Archaea that grows in deep-ocean sediment at 110 C

how much bacteria is there per gram of soil?

100,000

why haven't many bacteria been identified yet?

not cultured, need special nutrients, are part of complex food chains that require the products of other bacteria

what lab technique is usually used to uncover the presence of bacteria that can't be cultured?

PCR

two nutritional types of eukaryotes

• organic: molecule contains both carbon and hydrogen (CH4, glucose)
• inorganic: molecule contains only either carbon or hydrogen or neither (NaCl, H2O, CO2)
• energy (what's needed in addition to carbon source) can be obtained from light or chemical sources

autotrophism

do not require organic food, being able to live on just inorganic molecules, plus some energy source (can produce its own food)

• includes photosynthetic autorophism and chemoautotrophism

heterotrophism

"feeders on others" that need organic energy and carbon source

• includes chemoheterotrophism (which most medically important microbes fall under)

different methods to achieve heterotrophism

parasitism and saprophytism (live on dead organic molecules, especially in hosts with weak body defenses)

example of saprophyte

saprophyte feeding on a mushroom

what percent of fungi have been discovered so far? how many are pathogenic to us?

about 2%, 200 are pathogenic to us

mycology

study of fungi

mycosis

any diseases caused by fungus

mycelium

mold colony

do fungi-caused diseases tend to be acute or chronic?

chronic and are slow to develop

nutritional type and food acquisition method of fungi

strictly chemoheterotrophs (parasitic or saprophytic), absorptive

multicellularity and cellular arrangement of fungi

all (except yeasts), unicellular/filamentous/fleshy (filaments made of either aseptate/coenocytic or septate hyphae)

characteristic features and embryo formation of fungi

sexual (cell fusion) and asexual spores (cell division), none

do bacteria have spores?

mostly endospores, though some bacteria have asexual reproductive spores

cell wall and membrane composition of fungi

glucans, mannans, and chitin (polysaccharides) with sterols present in cell membrane

motility of fungi

none

oxygen requirement of fungi

aerobic (most molds) or facultative anaerobic (most yeasts)

dimorphism of fungi

• yeast in animal host at 37 C
• mold in soil at 25 C

ascospores

spores produced by an ascus (sac)

spherule

thick-wall body with spores

which mold species is aseptate?

rhizopus

which mold species produce ascospores?

penicillium and aspergillus

which is the only mold species to produce sporangiospores and zygospores?

rhizopus

which mold species has tubular hyphae?

Coccidioides immitis

which mold species is dimorphic?

Coccidioides immitis

mold species used most commonly for antibiotics

Penicillium

what mold is used most for decay?

Aspergillus sp.

hyphae of molds

• aseptate: Rhizopus
• septate: Penicillium and Aspergillus
• tubular: Coccidioides immitis

spores of molds

• sporangiospores and zygospores: Rhizopus
• conidia and ascospores (with sac): Penicillium and Aspergillus
• arhtroconidium and spherules in lungs: Coccidioides immitis

which mold most affects gardeners?

Aspergillus

morphology of yeast

non-filamentous single cells and are typically spherical or oval

how do yeast reproduce?

budding or fission

which yeast is known for baking and brewing?

Saccharomyces spp.

which yeast is known for causing candidiasis, vaginitis, and thrush?

Candida albicans

which yeast is part of normal flora/is an opportunistic pathogen?

Candida albicans, particularly problematic in infants, HIV infected, diabetes, and after antibiotics use

which yeast is resistant to phagocytosis?

Candida albicans

which yeast forms pseudohyphae?

Candida albicans

what disease does Cryptococcus neoformans cause?

cryptotoccosis (lung infection that spreads to central nervous system to cause meningitis)

how is Cryptococcus neoformans spread?

inhalation of contamined dried bird droppings and soil

what advantage does Cryptococcus neoformans have in being transmitted?

heavy polysaccharide capsule (rare in eukaryotes)

morphology of Cryptococcus neoformans

forms hypha and reproductive spores, dimorphic

which yeast used to be classified as protozoan?

Pneumocystis jiroveci

which yeasts are part of normal flora?

Candida albicans and Pneumocystis jiroveci

what disease does Pneumocystis jiroveci cause?

pneumocystis pneumonia especially in HIV and immunosuppressed patients

unique feature of Pneumocystis jiroveci

each tiny cyst containing eight developing parasites (found in sputum)

lichens

mutualistic relationship between algae (provides carbohydrates) and fungi (provides shelter/structure)