Microbiology of animals Flashcards
What are commensals?
microorganisms routinely found on the bodies of most healthy individuals, they usually colonize the body without causing an infection
where do we find specifically the most bacteria in the human body?
the gastrointestinal tract and more specifically in the colon.
why is the body of an animal adequate for bacteria to colonize?
it provides a wet, warm and potentially nutritious environment
what are the factors that influence the richness and abundance of the microorganisms of an individual? (4)
- temperature
- pH
- nutrient supply
- immune system (genetic factor)
As the animal develops, various body surfaces become progressively colonized: the individual acquires its _________.
normal microbiome
Why can commensals be beneficial? (3)
- teach the immune system
- provide host with vitamins and metabolic pathways (gut)
- provide protection against new incoming microbial populations (occupy the territory)
Why can commensals be paratism?
some commensals can become pathogenic under specific conditions (and commensals of one species may cause infectious diseases in another)
What are Microbial parasites that are able to cause infection?
pathogens
What is a situation in which a microorganism is established. and growing in a host, causing damage?
infection
What is a damage or injury to the host that impairs host functions? examples?
disease
ex: infectious disease, autoimmune disease, cancer
What is the ability of a parasite to inflict DAMAGE to the host?
pathogenicity
What is a measure of pathogenicity?
virulence
What causes disease only in the absence of normal host resistance? the normal microbiome contains them.
opportunistic pathogen.
What are herbivores?
animals that consume mostly plants
What are carnivores?
animals that consume mostly meat
What are omnivores?
animals that consume both plants and meat
Phylogenic studies suggest that herbivory has evolved _______ in many different lineages.
independently
Herbivores live on plant material rich in what?
cellulose and other insoluble polysaccharides (lignin, hemicellulose and pectin)
animals lack which enzyme that is required to degrade cellulose?
cellulase
Which microorganisms are able to degrade cellulose and what does it allow? how do we call this?
- the ones present in the gastrointestinal tract
- it allows the host to get the nutrients
- this mechanism is called mutualism, symbiotic relationship
What are the 2 digestive strategies that have evolved in herbivorous animals? explain.
- foregut fermentation: fermentation chamber precedes the acidic stomach
- hindgut fermentation: uses cecum and/or large intestine as fermentation chambers
What is the structure of the gastrointestinal tract of herbivores?
first: foregut fermentation chamber
followed by acidic stomach
then small intestine
followed by the cecum and large intestine (colon)
cecum + large intestine= hindgut fermentation chambers
what are examples of foregut fermenters?
ruminants, colobine monkeys, macropod marsupials, hoatzin
what are examples of hindgut fermenters?
cecal animals (horse, bunny), primates, some rodents, some reptiles
in ruminant animals, what happens to the food ingested?
it is minimally chewed, swallowed and passes into the rumen (foregut fermentation chamber)
the rumen is an ____ environment.
anaerobic
how is the pH of the rumen maintained?
maintained by saliva which contains sodium bicarbonate and sodium phosphate
how is fermentation in the rumen mediated?
- mediated by cellulolytic microbes that hydrolyze cellulose to free glucose and cellobiose that are then available to all microorganisms for growth
- the sugars are the fermented producing volatile fatty acids (acetic, propionic, butyric), ch4 and CO2
- fatty acids pass through the rumen wall into the bloodstream and are utilized by the animal as its main energy source.
A large portion of the rumen’s microorganisms produce cellulase. True or false?
False, only a small portion
Methanogens produce ____ and are strict ____.
CH4, anaerobes
_____ used by methanogens is not available to the host. up to 10% of the energy value of the feed can be lost as ____.
acetate; CH4
What inhibits methanogenesis and what does it reduce?
A compound called Monensin and it’a added to feed to reduce production of CH4
What happens after several hours of microbial digestion for ruminants? (2)
- small portions of the rumen contents are regurgitated well chewed and then swallowed again.
- smaller food particles are collected by the reticulum and moved to the omasum, where excess water is collected, which thens goes to the stomach (abomasum) and from there, to the intestines
the mass of microbial cells are subjected to digestion and serves as a major source of ______ and _____.
amino acids; vitamins
For non-ruminant herbivores, where does fermentation occur? and what does it provide?
in the cecum
it provides organic acids
For non-ruminant herbivores, what happens to the microbial mass that grows on cellulose and other polysaccharides?
they are no digested, and are excreted
As cellulose is excreted, animals with hindgut fermentation chambers have a _____ dietary requirement for amino acids and vitamins than ruminants do.
higher
what is coprophagy and what does it help?
it’s the consumption of faecal pellets and it overcomes the higher dietary requirement for amino acids and vitamins of non-ruminants.
Give an example of how animal-bacterial symbioses are established
a mutualistic symbiosis between the marine bacterium Aliivibrio fischeri and the Hawaiian bobtail squid:
the squid harbours. large population of the bioluminescent A. fischeri in a specialized structure. Bacteria emit light that resembles moonlight penetrating marine waters, which camouflages the squid from predators.
Transmission of bacterial cells is ______.
horizontal
What do termites do?
they decompose cellulose and hemicellulose
Termites have a diverse community of _____ including ________.
anaerobes (anaerobic bacteria); cellulolytic anaerobes (cellulolytic protists)
What are the 3 classes of rumen microorganisms?
Firmicutes
Bacteroidetes
Euryarchaeta
Firmicutes are ______ and within them we can find ______.
gram +
ruminococcaceae
Bacteroidetes are _____.
gram -
Euryarchaeta are mostly _______.
methanogens
Some rumen prokaryotes can either be _____ decomposers, _____ decomposers, _______ or______ decomposers
cellulose; starch; lactate; succinate
____ and ____ are fermentation products
lactate and succinate
The _____ product from one microbial metabolism is used for the input of another microbial metabolism in other organisms.
waste
What are characteristics of a normal microbiome for a human? (3)
- microorganisms usually found associated with human body tissue
- humans are colonized by microorganisms at birth
- normal microbiome changes over time and according to the condition of the host (diet, environment, age, sex, occupation)
What is the epidermis composed of?
of a inner layer of living, actively replicating cells and an outer layer of dead cells
What do sebaceous glands and apocrine sweat glands secrete and what effect does it have?
they secrete salt water, with various amounts of proteins, lipids, and sugars. They are slightly acidic and have some antimicrobial effects (lipids and proteins)
What does the dead cell layer prevent?
its a tough barrier that prevents microorganisms from penetrating deeper tissues
Why doesn’t the skin support growth of most microorganisms?
because its dry and is an acid environment
What are the ducts that carry secretions to the surface colonized with?
by a few well-adapted species (Gram +)
What does the normal microbiome of a human secrete?
it secretes bacteriocin that kills incoming competitors and protects to a certain extent, against colonization by harmful bacteria
The skin may also harbor ______: Propionobacterium acnes inhabits hair canals.
anaerobes (aerotolerant)
What is the normal microbiome of the skin composed of?
- yeasts, molds, bacteria
ex: mycobacterium, Staphylococcus and Streptococcus - primarily gram +: actinobacteria, firmicutes
What is the most abundant microorganism on sebaceous skin?
propionibacteria
What is the most abundant microorganism on moist skin?
- corynebacteria
- staphylococci
What is the most abundant microorganism on dry skin?
betaproteobacteria
The oral cavity is a complex, _______ microbial habitat. Both ____ and _____ niches are available.
heterogeneous
aerobic and anaerobic
What promotes localized microbial growth in the mouth?
high concentrations of nutrients near surfaces in the mouth
What does the teeth consist of?
mineral matrices (enamel) surrounding living tissue (dentin and pulp)
How do bacteria colonize tooth surfaces?
by first attaching to acidic glycoproteins deposited there by saliva
What happens when there’s extensive growth of oral microorganisms, especially streptococci?
results in a thick bacterial layer (dental plaque)
What happens is the presence of sucrose from diet?
STREPTOCOCCUS MUTANS synthesizes extracellular polysaccharides (dextran) that aid its attachment to the tooth surface (from an extracellular matrix, ECM)
As plaque continues to develop, ______ bacterial species begin to grow.
anaerobic
The microorganisms in dental plaque (S mutant and various lactobacilli) ferment sucrose and produce _____ that demineralizes the tooth enamel (solubilizes calcium)
lactic acid
Colonization of GI begins at _____. Microbial populations in different areas of the gastrointestinal tract are influenced by __________
birth
diet and physical conditions in the area
What does the acidity (pH 2) of the stomach and the duodenum of the small intestine prevent?
it prevents many organisms from colonizing the GI tract. Microorganisms in food particles might be protected
microorganisms in the human colon are ______ or _______. give examples.
strict anaerobes or facultative aerobes
ex: bacterioides, enteric bacteria, yeasts, anaerobic protozoa
What are the two main microorganisms in the human colon?
- firmicutes
- bacteroidetes
microorganisms digest _______ (cellulose, strach) and produce ____.
complex carbohydrates
Volatile fatty acids
What does the intestinal microorganisms of the large intestine ferment? and what do they produce?
volatile fatty acids
they produce gas (CO2 and H2)
___________ and organisms that can ferment _____ and ______ produce H2S. _______ are responsible for the smell
Sulfate reducers
cysteine and methionine
organosulfur compounds
What do intestinal microorganisms carry out? examples
a variety of essential metabolic reactions that produce various nutrients that benefit the host.
ex: amino acids, vitamins (K, thiamine, riboflavin)
Microorganisms contribute to the _____ of the gastrointestinal tract
maturing
What do microbes in the gut affect? what can they play a role in?
- early development, health, and predisposition to disease
- obesity
The microbiome of the nose and nasopharynx is very similar to which microbiome? What does it consist of?
the mouth
- staphylococci, streptococci, corynebacteria
Nasopharynx may harbor potential pathogens that are under control by what? what are they? (3) HEALTHY CARRIER
the host immune system
- Streptococcus pneumoniae
- Haemophilus influenzae
- Neisseria meningitidis
the lower respiratory tract (trachea, bronchi and Lungs) is free of microorganisms in healthy individuals. True or False?
False, it used to be considered that until research has found that the tract harbours a microbiome of low biomass
Why are the genitourinary tract of men and the urinary tract of woman generally free of microorganisms?
due to flushing action of urine
what can cause potential pathogens in the urethra to multiply and cause disease?
altered conditions like change in pH
A few of normal microorganisms of GI tract can cause urinary tract infections. True or False?
True such as E. coli and Proteus mirabilis
____ control de glycogen concentration of the vaginal epithelium.
hormones
microorganisms degrade glycogen and produce _____ which causes what?
lactic acids which reduces the pH off the vaginal tract to 4.5
What are the characteristics of the vaginal tract before puberty/after menopause?
- glycogen: low
- pH of vaginal secretion: Alkaline
- Microbial flora: staphylococci, streptococci, coliform, corynebacteria
What are the characteristics of the vaginal tract sexually mature?
- glycogen: high
- pH of vaginal secretion: acidic
- Microbial flora: lactobacilli, streptococci, corynebacteria, Candida albicans
What are the (usually) sterile zones? (7)
- blood
- spinal fluid
- internal portion of urinary tract (bladder, kidney)
- peritoneal cavity (gut cavity)
- pleural cavity (lung cavity)
- sinuses
- interior region of other body tissues (bones, muscle,..)
