bacteria: gram positive or gram negative

gram positive bacteria

• cell envelope contains one membrane (monoderms)

• two phyla:

  • firmicutes

    • low G + C (guanine and cytosine): (26-60%)

  • actinobacteria

    • high G + C (guanine and cytosine): (60-80%)

• third phylum

  • tenericutes

    • no cell wall → pleomorphic, resistant to cell wall targeting antibiotics

which came first gram positives or gram negatives?

• came first and then some gram positives acquired an outer membrane and became the gram negatives

• gram negatives came first then loss of outer membrane led to emergence of gram positives

firmicutes (low guanine and cytosine)

• clostridium

• bacillus

• staphylococcus

• streptococcus

• listeria

• lactobacillus

• mycoplasma

clostridium

• anaerobic

• produce ATP by fermentation or anaerobic respiration

• endospore forming

• tetanus, botulism, intestinal, and food poisoning

bacillus

• aerobic

• endospore forming

• soil inhabitants

  • some produce antibiotics such as bacitracin and polymyxin

• food poisoning, anthrax

• not transmittable

staphylococcus

• facultative anaerobe

• skin, skin glands, mucous membranes

• staph. epi. : normal flora of skin

• staph. aurens: nasal membranes, skin, GI tract

  • virulence factors:

    • coagulase: fibrin clot formation

    • beta hemolysis: complete lysis of RBCs

    • DNase: destroys DNA

• readily engage in HGT

• transmittable

streptococcus

• cocci in chains

• faculatative and strict anaerobes

• lancefield grouping system used for clinical diagnosis

  • based on antibody and microbe agglutination reactions

• some are transmittable

  • strep pyognes: strep throat, Gp-A beta hemolytic

  • strep pneumoniae: lobar pneumonia, no Gp

listeria

• L. monocytogenes = listeriosis

  • foodborne → cheese, milk, meat, poultry, vegetables, ice cream

  • disease may not appear until after 5 weeks so source of infection difficult to find

• saprophytic and widespread in nature

• targets immunocompromised

  • pregnant, newborns, elderly

• not transmittable

lactobacillus

• fermentation only (no ETC)

  • produce lactic acid

• widespread in nature → foods they ferment

  • food production → yogurt, cocoa, coffee

• normal flora in the mouth, GI, and genital tract

  • acquired soon after birth

  • producing small antibacterial peptides → bacteriocins

  • some have formation of dental caries → cavity formation

mycoplasma

• no cell wall

• causes walking pneumonia

• transmittable

actinobacteria (high guanine and cytosine)

• streptomyces

• actinomyces

• corynebacterium

• mycobacterium

• propionibacterium

• gardnerella

• bifdobacterium

streptomyces

• soil inhabitants produce geosmin (smell of dirt)

• produces 70% of all antibiotics (erythromycin, neomycin, streptomycin, ivermectin)

• found on a japanese golf course

• produces avermectin

  • streptomyces myrophorea: named because it smells like oil of wintergreen

  • found on alkaline soil in northern ireland

actinomyces

• fungal like growth → make aerial spores

  • spores sit on top of aerial hyphae

• found in soils & sediments

• famous for production of wide variety of industrially and medically relevant compounds such as:

  • antibiotics

  • chemotherapeutics

  • fungicides

  • herbicides

  • immunosuppressants

    • 70% of all antibiotics

• normal oral/GI flora

• actinomycosis is opportunistic

• not transmittable

corynebacterium

• causes diphtheria

  • pseudomembrane formation in throat

  • diptheria toxin produced by a lysogenic phage

• snapping division of cells & barred or bowling pin staining pattern

• toxin from prophage

• transmittable

mycobacterium

• acid fast

• aerobic

• soil organism so can be saprophtyic

• mycolic acid outer layer (biological wax) makes cells resistant to envrionmental changes such as drought

  • also slows the penetration of antibiotics into pathogenic cells

• some pathogens: zoonotic & transmittable

  • M. bovis, M. tuberculosis & M. leprae

  • BCG vaccine is live attenuated M. bovis & used to vaccinated children in areas with high TB

    • also used to treat early stage bladder cancer

• slow growing (2-40 days)

propionbacterium

• skin & digestive tracts of animals

• anaerobic

• produces propionic acid by fermentaiton

• p. freudenreichii: eye formation and aroma in swiss cheese holes

• p. vulgaris: acne and body odor in humans

gardnerella

• normal vaginal flora or urogenital tracts

• 85-90% of women

• overgrowth → vaginosis

• due to:

  • depletion of lactobacillus in the vagina (pH at or below 4.5)

  • hormonal fluctuations

  • physiology

  • sometimes lifestyle

    • self limiting

bifidobacterium

• fermentation products are acetic lactic acid

• mouth and intestines of warm blooded animals

  • fecal material

  • pioneer GI colonizer in breastfed infants

• found in activia (yogurt) /align (probiotic)

sequelae

disease condition that remains after the pathogen is gone

auxotrophy

organism cannot synthesize a required nutrient

communicable

spreads person to person

acid fast

mycobacteria stain this way due to mycolic acid

stickland reaction

clostridium ferments amino acids, produce decay odors

firmicutes name origin

• firmus: strong

• cutis: skin

• → tough cell wall

• some have pseudo-outer membranes and stain gram-negative despite being firmicutes

actinobacteria background

• one of the largest taxonomic unit recognized within the domain Bacteria

• widespread free living saprophytes in soil and sediments

  • some are important pathogens

  • some grow like fungi

  • some produce aerial spores

  • some have an outer layer of mycolic acid on their cell walls

• higher GC + thicker cell walls = survive harsher environments

• short list of more well known actinos:

  • actinomyces: opportunistic pathogen

  • streptomyces: pharmaceutically important

  • corynebacterium: some pathogens

  • mycobacterium: some pathogen

  • propionibacterium: opportunistic pathogen & food production

  • gardnerella: opportunisitic pathogen

  • bifidobacterium: activia

streptococcus classification details

• lancefield grouping system uses anitbody agglutination reactions

• three hemolysis types:

  • alpha → partial

  • beta → complete

  • gamma → none

• s. pyogenes = group A, beta hemolytic

• sequelae of strep throat: rheumatic fever and acute glomerulonephritis

lactic acid producing bacteria

• streptococcus pyogenes: strep throat, glomerulonephritis, rheumatic fever

• streptococcus pneumoniae: lobar pneumonia, ear infections

• streptococcus mutans: dental caries

• enterococcus faecalis: opportunistic pathogen (UTI infections)

• lactococcus lactis: production of buttermilk, cheese, sour cream