microbiology of animals

what are commensals

what are commensals

microorganisms routinely found on the bodies of most healthy individuals

why are animals good microbial habitats

warm, wet, nutritious

temperature pH, nutrients, influence and impact

relationships b/w animals and microorganisms

can be commensals (take advantage of but do not harm host)

can be beneficial (protection, vitamins, teach immune system)

can be parasites (under specific conditions)

where are most microorganisms found in animals

the GI tract

microrganisms in herbivores

in Gi tract - degrade cellulose and provide host with nutrients

what are the two types of digestion in herbivores

foregut fermentation (chamber precedes stomach) and hindgut fermentation (cecum or large intestine)

characteristics of the rumen

anaerobic environment

minimally chewed food

pH is maintianed by saliva (sodium bicarbonate and sodium phosphate)

how does the rumen ferment

cellulolytic microbes hydrolyze cellulose to free glucose and cellobiose, that are then available to all microorganisms for growth

sugars are fermented to volatile fatty acids which pass into the bloodstream as an energy source

material is rechewed and sent to the stomach - microbial cells are subjected to digestion and are a source of AA and vitamins

rumen microorganisms

ciliated protozoa, bacteria, archaea

ruminococcus (watch recording)

what is the role of methanogens

uses acetate that the animal can’t

what is added to feed to reduce CH4 production

monensin (inhibits methanogenesis)

how do non-ruminant herbivores ferment

in the caecum, generates organic acids

microbial masses are not digested, so these animals do not get as much AA and vitamins so they need more food

how do rabbits attain their AA and vitamins if they aren’t ruminants

coprophagy - eating their own poop

hawaiian bobtail squid and Aliivibrio fischeri symbiosis

mutualistic

squid keeps the bacteria in its light organ (it is bioluminescent)

bacteria emits light that camouflages squid from predators

transmission of bacterial cells is horizontal

termites

decompose cellulose and hemicellulose

anaerobes and cellulolytic anaerobes

uses anaerobic bacteria and cellulolytic protists

what is happening in a normal human microbiome

microorganisms are associated with human body tissue

colonized at birth

microbiome changes over time

what is the role of the sebaceous glands and apocrine sweat glands

secretes salt water with various amounts of proteins, lipids, and sugars

slightly acidic and have some microbial effects

skin microbiome

dead cell layer prevents microorganisms from getting deeper in tissues

ducts that carry secretions to the surface are colonized by a few (gram positive) species

skin may harbour anaerobes but aerotolerant bacteria

why does the skin not often support the growth of microorganisms

it is dry and acidic

what does the normal skin microbiome secrete to reduce harmful bacteria colonization

bacteriocin

oral cavity microbiome

heterogeneous habitat (aerobic and anaerobic)

high nutrient concentration

teeth are mineral matrices surrounded by living tissue

how do bacteria colonize oral microbiomes

colonize tooth surfaces (attach to acidic glycoproteins from saliva)

they grow and generate dental plaque (bacterial layer). Sugar from the diet help attachment to tooth (forms ECM)

with more plaque, more anaerobic bacteria can grow

microorganisms in dental plaque

S. mutans and lactobacilli

ferment sucrose and produce lactic acid that demineralizes the tooth enamel.

what influences the different microbial populations in different areas of the GI tract

diet and physical conditiosn of the area (stomach acidity)

what prevents organisms from colonizing the GI tract

high acidity of the stomach and duodenum

microbiome in human colon

mostly strict anaerobes or facultative aerobes

(examples on slides)

high variability in gut communities between different individuals

microorganisms in the human colon

digest complex carbohydrates and produce VFAs

large intestine ones - ferment VFAs and produce gas, methanogens convert CO2 and H2 to CH4

carry out essential metabolic reactions to generate nutrients for the human

contribute to maturation of the GI tract

microbiome of respiratory tract

similar to mouth

staphylococci, streptococci, corynebacteria

upper respiratory tract

nasopharyn may harbour pathogens that are under control by the host immune system

lower respiratory tract

historically considered free of microorganisms, but is now considered to have a low biomass microbiome

genitourinary tract

generally free of microorganisms (due to urine flushing - mens tend to be cleaner because of longer uretha)

altered conditions can cause potential pathogens in the urethra

some GI microorganisms can cause UTIs

vaginal tract

microorganisms degrade glycogen and produce lactic acid which reduces of the pH of vaginal tract

what are normally considered sterile zones

blood, spinal fluid, internal portion of urinary tract, peritoneal cavity (gut - considered an outside zone), pleural cavity (lung), sinuses, interior region of other body tissues (bones, muscles, etc)