12- Animal Microbiology Flashcards
Commensals
microorganism routinely found in healthy individual
Do not cause infection
Animals as microbial habitats
Exposure: from the environment, other animals, food, and water. Animal bodies provide: - heat - water - nutrition for adapted bacteria
Factors influencing animal microbiomes
temperature pH nutrient supply immune system (genetic factor and others as animals develop their microbiomes develop with them
Commensals
use the host for nutrients and shelter without causing harm
may be beneficial or become parasitic
beneficial commensals
Provide the host :
- with vitamins and metabolic pathways
- protection from incoming microorganism
- immune system practice
parasitic commensals
commensal may become parasitic under specific conditions.
Commensals of one species may be pathogens to another
Pathogens
microbial parasites what are able to cause infection
Infection
situation in which a microorganism is established and growing in a host, causing damage
Disease
damage or injury to the host that impairs host function
infectious disease, autoimmune disease, cancer, ect
Pathogenicity
the ability of a parasite to inflict damage to the host
Virulence
measure of pathogenicity
Opportunistic pathogen
causes disease only in the absence of normal host resistance.
contained within the normal microbiome
Gastrointestinal tract of animals
contain the vast majority of the microbiome
Cellulose
insoluble polysaccharide
cannot be directly digested by animal due to las of cellulase
Cellulase
enzyme which degrades cellulose
Herbivores diet
rich in cellulose, lignin, hemicellulose, pectin and other insoluble polysaccharides
-> digested by microorganism in the GI tract (mutualism/symbiotic relationship)
Digestive strategies: Cellulose
Foregut fermentation: fermentation chamber proceeds the acidic stomach
Hindgut fermentation: uses cecum and/or large intestine as fermentation chambers
the Rumen
Present in ruminant animals
a.k.a. the foregut fermentation chamber
Food is minimally chewed, swallowed -> rumen
- ranges in capacity
-39-40C
- pH: 5-7 maintained by saliva containing sodium bicarbonate and sodium phosphate
- ANAEROBIC
Rumen microorganisms
only a small proportion are cellulase producing
Fermentation is regulated by cellulolytic microbes
Cellulolytic microbes
hydrolyze cellulose -to-> free glucose and cellobiose
products are now available for other microorganism growth
sugars are then fermented -> volatile fatty acids, CH4 and CO2
Fatty acids : pass through the rumen wall into the blood stream as main energy source
Methanogens
strict anaerobes
produce CH4
4H2+CO2->CH4+2H2O + Energy
CH3COOH (acetate)->CH4+CO2+Energy
acetate is not avialable to the host: 10% of feed is lost energy
Monensin
inhibits methanogenesis
added to fee to reduce CH4 production
Rumens and regurgitation
after a few hours small portions of the rumen contents are regurgitated, chewed, and swallowed
smaller food particles are collected in the reticulum -then-to-> the omasum
Omasum
recieves contents of the rumen afte rthe reticulum
collects ecess water
moves next to the abomasum
Abomasum
a.k.a. stomach
the mass of microbial calls which gigested cellulose are now in term digested : major source of amino acids and vitamins
contents now move to the intestine
Non-ruminent animals
Fermentation of cellulose : in the caecum
the microbial mass that grows on cellulose is not digested: it is excreted
Higher dietary requirement for amino acids and vitamins
Caecum
provides organic acids to the animal
location of cellulose fermentation in non-ruminent animals
