gut microbia Flashcards
microbiota
collection of all microorganisms living in a particular envir
* ~500,000 species
* contribute to 1-3% of body mass (~1kg of body weight)
* collectively ≥100x genes than host
* can perform fx host cannot
commensalism
symbiotic relationship where 1 benefits & other neither benefits nor is harmed
microbiome
microbes, their genetic elements, & interactions with their envir
* who’s there & what they’re doing there
metagenome
whole genome sequencing
human microbiome project
- establish a reference database for
- oral
- skin
- gut
- vaginal
- nasal/lung
- 10,000 species
- metabolic activities
- dynamic
amplicon sequencing
identify bacteria by sequencing 1 region of their genome
* who is there
gut microbiota
- influenced by:
- diet
- abx ➞ will disrupt
- disease
- age
- genentics
- amount & types change over length of GIT
- aerobic org in upper GIT
- anaerobic org in lower GIT
gut microbia fx
metabolic:
- competition for space & nutrients
- vit & AA synthesis
- carb fermentation ➞ short-chain fatty acid synthesis (SFCA) ➞ energy
- secrete antimicrobials
protective:
- suppress pathogen growth
- colonization resistance
- innate & adaptive immunity
structural & histological:
- villi & crypt development ➞ growth of enterocytes
- mucus layer
- permeability
microbes in rumen digestion
- make volatile fatty acids (VFAs) (aka short chain fatty acids (SCFAs)
- must use glucose to propagate ➞ produce VFAs as byproducts that ruminants use
-
propionate (propionic acid) CH₃CH₂COOH ➞ converted to glucose in liver
- primary source of glucose in liver
- butyrate (butyric acid) CH₃CH₂CH₂COOH ➞ converted to energy
-
acetate (acetic acid CH₃COOH ➞ converted to energy
- protein synthesis ➞ muscle
- fat synthesis ➞ adipose
- fat & lactose synthesis ➞ mammary gland
- break plant polysaccharides into simple sugars
- use glucose as energy source to grow
- VFA are end-products
- source or energy for cow
- bacteria make protein ➞ modify dietary fats (triglycerides)
- hydrolysis: break TAG to FA & glycerol
- biohydrogenation: FA saturated
- fat ingested ≠ fat put into circulation
- more chewing = higher amounts of forage
- chewing makes saliva ➞ keeps acid levels good
VFAs
volatile fatty acids aka short-term fatty acids (STFAs)
- byproducts of microbial fermentation of glucose (microbes use glucose as source of energy)
-
cows use VFAs as energy source
- propionic acid aka propionate ➞ primary source of glucose
- acetic acid aka acetate
- butyric acid aka butyrate
- acetate & butyrate used for fat synthesis & energy
non-ruminants & SCFAs
- dietary & endogenous carbohydrates
- proximal colon:
- high substrate concentration
- active bacterial growth
- carbodyhdarte fermentation
- high SFCA production
- distal colon:
- low substrate concentration
- slow bacterial growth
- protein fermentation
- SFCA ➞ intestinal epithelium & immune system
influences on VFAs
- diet & rumen pH influences amount & ratio of VFA
- pH > 6 favors fiber digesters (cellulolytic bacteria)
- pH < 6 favors starch digesters (amylolytic bacteria)
- pH < 5 depresses protozoa
- acidosis ➞ animal cannot use forage
- eating a lot of starch makes more VFA to influence pH
- microbes use energy to grow ➞ make protein & AA
- microbes = source of proteins an can use
antimicrobial peptides
-
paneth cells in crypts produce defensins & cryptidins
- enzymes that disrupt bacterial membranes to prevent them from growing
- lysozyme in tears & saliva = enzyme that breaks bond in bacteria cell wall
- makes wall leaky ➞ cannot grow
metabolic function of gut microbia
- vit & AA synthesis
- carb fermentation ➞ short-chain fatty acid synthesis (SFCA) ➞ energy
- secrete antimicrobials
- competition for space & nutrients
protective function of gut microbia
- competition for space & nutrients
- secrete antimicrobials
- suppress pathogen growth
- colonization resistance
- innate & adaptive immunity
