Lecture 2-10 - Lecture 10- Diversity: Bacteria 3/7/2011...

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Lecture 10- Diversity: Bacteria 3/7/2011 © Nicola Davies 2011 Diversity: Bacteria A Look at 2 Species Lecture 10 March 9, 2011 2 B13: Firmicutes Mycoplasma lack cell walls and do not stain Round or rod shaped Very large phylum Less diversity than proteobacteria Many species in just 6 genera Common characteristic: clustering of 16S rRNA sequences Major component of gut flora Exist in equilibrium with Bacteriodetes Ratio differs based on weight and changes on weight loss 3 Who Am I? 4 Listeria monocytogenes Gram-positive, non-spore forming, rod-shaped bacterium Synthesizes peritrichous flagella at temperatures up to 30°C Responsible for the food borne illness, listeriosis Symptoms are variable from mild gastro-intestinal illness to serious complications such as meningitis, septicemia, spontaneous abortion/stillbirth Annually in USA, 2500 cases of illness and 500 deaths second highest fatality rate (20%) and the highest hospitalization rate (90%) for foodborne illness Major symptoms of disease are restricted to pregnant women, neonates, the elderly, others with compromised immune systems Far more infections likely occur but are asymptomatic Estimated that 10% of humans are carriers Important agricultural disease causing spontaneous abortion in ruminants Animals also act as carriers 5 L. monocytogenes - Survival Widespread in the environment: soil, healthy and decaying vegetation , water, intestinal flora of many animals Widely found in food processing environments (air, drains, floors, machinery ) Faculataively anaerobic Halotolerant: salt levels up to 16% Wide pH range: 4.2-9.6 Psychrotrophic: minimum growth temperature of -0.4 °C Spoilage dates assume storage below 4.4°C Only 73% of retail and 40% of home refrigerators below 5 °C 3% of commercial grocery refrigerators operate in the 15 17 °C range Survives for long periods of time in the environment, on foods, in processing plants, in household refrigerators Can remain viable on food contact surfaces for days or weeks Easily killed by thermal treatments (cooking)
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Lecture 2-10 - Lecture 10- Diversity: Bacteria 3/7/2011...

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