Animal Microbiology Part II Flashcards
Skin layers
First line of defence against pathogens
Epidermis: outer layer of dead skin and inner layer of actively replicating cells
Dermis: sebaceous glands, apocrine sweat glands secrete water, salt, protein, lipids (antimicrobial) and sugars
- anaerobic environment in the glands
Skin as an environment
Healthy skin is a dry, acidic environment which does not support growth of many microbes
- microbes that do survive secrete bacteriocidin to prevent growth of others
Ducts are colonized by gram-positive adapted species
Propionobacterium acnes may inhabit hair canals
Sebaceous skin is highest in which microbe?
Moist skin? Dry Skin?
Sebaceous skin highest in propionibacteria
Moist skin highest in Corynebacteria and Staphylococci epidermis
Dry skin highest in Betaproteobacteria and Corynebacteria
Teeth structure and habitats
Teeth consist of enamel mineral matrices surrounding dentin and pulp (center) living tissue
Dental plaque is a thick layer of bacterial growth
Aerobic niche: enamel surface, Streptococcus mutans consumes sucrose from the diet and produces dextran to aid attachment to surface to continue forming plaque
Anaerobic niche: plaque S. mutans and lactobacilli ferment sugars and produce lactic acid which demineralizes tooth enamel
Microbes in GI tract
Stomach and small intestine (pH 2-5) - helicobacter can grow in this low pH environment and food particles can protect other bacteria
Colon (pH 7) - fermentation chamber, strict or facultative anaerobes
- Bacteroidetes, E. coli, yeasts, anaerobic protozoa (Enamoeba coli) - highly variable diversity between people
- Ruminococcus and methanogens
Microbial digestion in the colon
Microbes digest CHO —> VFAs
Microbes in the colon ferment VFAs —> CO2 + H2
In 1/3 of adults methanogens convert CO2 + H+ —> CH4
Sulfate reducers ferment Cys and Met —> H2S, methanethiol (smelly)
Microbes can also produce AA, B12, vitamin K, thiamin and riboflavin which can benefit host
Respiratory tract microbes
Nose and nasopharynx: Streptococci, Staphylococci, Corynebacteria
- but nasopharynx may carry pathogens under control by immune system
Lower respiratory tract (trachea, bronchi and lungs) have a low biomass microbiome
Genitourinary tract microbes
Genitourinary tract of men and urinary tract of women generally free of microbes due to urine flushing
- change in pH can lead to urinary tract infections
- urethra is more narrow in women and more prone to infection
Vaginal tract: microbes degrade glycogen —> lactic acid to keep pH low
Generally sterile zones in the body
Blood, spinal fluid, bladder + kidney (interior urinary system), peritoneal cavity (gut cavity), pleural (lung) cavity, sinuses, interior regions of other body tissues such as bone and muscle
