ch 13
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human microbiota
the microorganisms living in our body sites - gut microbiota, skin microbiota
human microbiome
the microbial community in the human ecosystem -used to be called resident, indigenous, and normal flora
areas in the body that are colonized by microbiota
skin, upper respiratory tract, gastrointestinal tract, outer opening of urethra, external genitalia, vagina, external ear canal, external eye lids
areas of the body that are relatively “free of” microorganisms in a healthy individual
all internal tissues and organs -heart -liver -kidneys and bladder -brain and spinal chord -muscles -bones -ovaries, testes -glands (pancreas, thyroid, salivary) -sinuses -middle and inner ear -internal eye fluids with in organ or tissue -blood -urine -cerebrospinal fluid -saliva prior to entering oral cavity -semen prior to entering urethra -amniotic fluid surrounding fetus
which part of the body harbors the most microbes?
colon (large intestine)
what are SCFAs? How are they produced?
SCFAs= short chain fatty acids -produced by fermentation of dietary fibers by the gut bacteria
2 examples of beneficial effects of microbiota on human health
• Lactobacillus (good bacteria) in vagina can inhibit overgrowth of yeast and bacterial pathogens • SCFAs that are produced by gut bacteria can supply energy to epithelial cells in large intestine, anti-inflammatory, etc
what is a germ free animal?
an animal that has no microorganisms living in or on its body
do germ free animals have the same physiology as normal animals?
No
what is dysbiosis?
occurs when there is an imbalance (either in number or type) of microbial communities colonizing the host, leading to changes in microbial functional composition and metabolic activities -can result in diseases
what are the two most abundant bacteria phyla in the mouse gut?
Firmicutes and Bacteroides (90% of all bacteria)
How did the obese mice differ in the ratio of the two bacterial phyla when compared to lean mice?
Firmictues (G+) were the more abundant phylum in obese mice, but Bacteriidetes (G-) were more abundant in lean mice
what happened to the lean (normal) mice when they received fecal transplant from obese mice?
-The lean mice gained more body fat -This shows that microbiota from obese mice can promote fat accumulation in a previously lean host.
examples of modern lifestyle and practices that can contribute to decreased microbiota
-clean water -smaller families -c section -forumla feeding -amalgam dental fillings -antibiotic use
how and when does a newborn begin to acquire microbiota?
initial colonization occurs during and 8 to 12 hr after delivery -exposure to maternal birth canal or fecal microbiota -feeding -human contact
beneficial bacterial genus that are the pioneer colonizers of infants but decreases in number as we age
bifidobacterium
bacteria commonly used as probiotic food or supplements
Bifidobacterium and Lactobacillus
difference between probiotic and antibiotic therapy
probiotic therapy:Using beneficial bacteria to promote healthy metabolism and to suppress the overgrowth of some pathogens antibiotic therapy:Using drugs to kill pathogens, can disrupt the normal microbiome composition, lead to loss of beneficial bacteria and superinfections
characteristics of microorganisms found in the large intestines
abundance: Trillions, largest in the body Oxygen: Mostly strict anaerobes; few facultative anaerobes (E. coli) Metabolism: Ferment undigested food produce SCFAs, vitamins, gas Host benefits: Nutrient absorption, vitamin production, recycle bile salts Health impact: Influence lactose tolerance, obesity, IBD
oral microbes that are responsible for dental caries
Streptococcus mutans
how does Streptococcus mutant adhere to teeth?
It uses dietary sugar to make dextran slime layer to colonize tooth surface
what is known about lactobacilli’s role in the reproductive tract of pre- menopausal women?
Role of Lactobacillus in vaginal health: Help create a healthy acidic pH in women’s vagina and prevent bacterial and yeast infections High estrogen → more glycogen → feeds Lactobacillus → Lactobacillus makes lactic acid → low pH → protects against infection.
why are women more likely to get a urinary tract infection (UTI) than men?
urethra is shorter & closer to bladder, prone to infections
to diagnose a UTI, why do we need to use the “midstream” catch (“clean catch”) method to collect urine samples?
fewer contaminants → more accurate detection of real UTI-causing bacteria.