Microbial Ecology • The study of microorganisms and their environment. www-esd.lbl.gov
Symbiosis • “living together” • Describes the interactions that occur between two dissimilar organisms (usually 2 different species) that live together or are in close association with one another. • Symbionts • the organisms that live together in such a relationship.
Neutralism • Symbiotic relationship in which neither symbiont is affected by the relationship. • Both species are unaffected.
Commensalism • Symbiotic relationship in which one symbiont benefits and the other species is not affected (neither harmed nor helped). • Ex. Propionibacterium • many species in this genera live on the skin and are thought to neither hurt nor help humans. • Host • An organism that harbors another organism.
Mutualism • Symbiotic relationship that is beneficial to both symbionts. • Ex. Termites and protozoa • Ex. Lichens • Ex. Some species of our microflora (i.e. Escherichia coli.) Termite Lichen. botit.botany.wisc.edu E. coli. www3.niaid.nih.gov
Parasitism • Symbiotic relationship in which one symbiont is benefited and the other is harmed. • Ex. Sheep liver fluke • Ex. Opportunistic pathogens of our normal flora. Sheep Liver Fluke.locksparkfarm.wordpress.com
Synergistic Relationship • When two (or more) microorganisms “team up” to cause a disease that neither could cause by itself. • Called synergistic infections. • Ex. Acute necrotizing ulcerative gingivitis (i.e. “Trench Mouth). Acute necrotizing ulcerative gingivitis. www.ohiohealth.com
Normal Flora of Humans • All microbes that reside on and within a person. • Most commonly inhabited parts of the body. • Eyes • Skin • Mouth • Ears • Upper respiratory tract • Gastrointestinal tract • Genitourinary tract www.scq.ubc.ca
Establishing Normal Flora www.solarnavigator.ne www.ehponline.org
Transient Flora • Live temporarily on the body. • Often “picked up” from our daily routines. • Why are they temporary?
Importance of Normal Flora • Often helps prevent infection. • Prolonged use of antibiotics can cause an imbalance. • Ex. Candida albicans Candida albicans. www.humanillnesses.com Candida albicans infection. www.lib.uiowa.edu
Microflora of the Skin • Consists of mostly bacteria and fungi. • Most are anaerobes, although some are aerobic. • Anaerobes live in the: • deeper layers of the skin • hair follicles • sweat and sebaceous glands health.howstuffworks.com
Microflora of the Skin • The number and variety of microorganisms depends on the: • Amount of moisture present • pH • Temperature • Salinity • Presence of chemical wastes such as urea and fatty acids • Presence of other microbes (which may produce toxic substances)
Groups of Normal Skin Flora • 1. Diphtheroids (Coryneforms) • Gram-positive, non-spore forming rods. • Ex. Propionibacterium acnes. • 2. Staphylococcus spp. • Gram-positive cocci usually arranged in clusters. • Helps maintain normal flora balance. • 3. Yeasts – Candida spp. • Single-celled fungi. • Ex. Causes tinea versicolor. Propionibacterium acnes. bacteriality.com Tinea versicolor. georgiahealthinfo.gov
Microflora of the Eyes and Ears • Ears • Middle ear and inner ear sterile. • Outer ear and auditory canal contain same types of microorganisms as are found on the skin. • Eyes • Does contain some microorganisms. • Tears, mucus, and sebum that are produced in and around the eye greatly reduce many microorganisms. www.bluedothealth.com www.infovisual.info
Respiratory Tract • Upper Respiratory Tract • Nasal passages • Throat (pharynx) • Lower Respiratory Tract • Larynx (voice box) • Trachea • Bronchi • Bronchioles • Lungs www.uic.edu
Microflora of the Respiratory Tract • Upper Respiratory Tract • Nasal Passages and Throat • Have many species of microorganisms. • Provide moist, warm environment. • Many are harmless. • Some are opportunistic pathogens. • Some people are carriers of virulent pathogens. • Lower Respiratory Tract • Usually microbe free.
Microflora of the Upper Respiratory Tract • Staphylococcus spp. • Gram-positive cocci in clusters. • Often includes S. aureus. • Corynebacterium spp. • Gram-positive rods; nonmotile; nonspore-forming. • Nonpathogenic species. • Collectively called diphtheroids. • Moraxella spp. • Gram-negative diplococci. • Resemble Neisseria species. S. aureus Corynebacterium spp. Moraxella spp.
Microflora of the Upper Respiratory Tract cont. • Haemophilus spp. • Small, gram-negative rods. • Often includes H. influenzae. • Bacteroides spp. • Small, gram-negative rods. • Strict anaerobes. • Streptococcus spp. • Gram-positive streptococci in chains. • Often includes S. pneumoniae. H. influenzae Bacteroides fragilis Streptococcus spp.
Microflora of the Oral Cavity • Provides great shelter and nutrients for many species of microbes. • Flourish in gum margins, crevices between teeth, and deep fold of the tonsils. • Bacteria feed on food particles and dead epithelial cells. • Poor hygiene can lead to periodontal diseases. • Most common microbes are species of alpha-hemolytic streptococci. anatomy.med.umich.edu
Gastrointestinal Tract • Digestion of food, absorption of nutrients, and elimination of undigested material. • Includes: • Oral cavity and throat (already discussed) • Esophagus • Stomach • Small intestines • Large intestines • Anus www.giconsults.com
Microflora of the Gastrointestinal Tract • Stomach • Acidic environment prevents much growth. • Exception – Helicobacter pylori – found in some people causes ulcers. • Small Intestine • Upper part of small intestine (duodenum) – little growth due to bile. • Lower portion of small intestine (jejunum and ileum) – more microbial growth present. • Large intestine (colon) • Contains the largest number and variety of microbes. • 500-600 species. • Anaerobic environment. • Contains obligate anaerobes, aerotolerants, and facultatives. • Many are opportunistic pathogens if enter other areas of the body.
Genitourinary Tract • Urinary Tract • Kidneys • Ureters • Urinary bladder • Urethra • Male and Female Reproductive Systems www.pvurology.org
Microflora of the Genitourinary Tract • Healthy kidneys, ureters, and urinary bladder are sterile. • Urethra harbors many microbes (i.e. yeasts, bacteria, and viruses). • Usually don’t invade bladder due to acidic nature of urine. • UTI (urinary tract infections) occur when microbes travel up the urethra and multiply. • Male and female reproductive systems are sterile with the exception of the vagina. • Type of growth depends on stage of sexual development. • pH of vagina changes throughout sexual development providing different environments for different organisms.