Lecture 6 growth

Lecture 6 growth - Vreeland RH, Rosenzweig WD, Powers DW....

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Some microorganisms form resistant structures called spores when exposed to adverse conditions. These spores have been found to survive for hundreds and even thousands of years under the proper conditions. Researchers now believe they have isolated halophilic (salt-loving) bacterial spores that were trapped in brine "bubbles" as the salt in the ancient sea evaporated. If true, these organisms are the oldest ever discovered (220-250 million years old). The previous "record" was from the mid-1990s with detection of bacterial spores in a bee preserved in amber 25–40 million years old. Intact salt crystals were carefully collected from the walls of the waste isolation pilot plant’s air intake shaft (The Waste Isolation Pilot Plant, or WIPP, is the world's first underground repository licensed to safely and permanently dispose of transuranic radioactive waste left from the research and production of nuclear weapons) at a depth of 569 meters (1867 feet) below the surface. The nearly pure salt crystals contained fluid inclusions (tiny openings inside the crystals that contain a mixture of saturated brine and nitrogen). After thoroughly sterilizing the surface of the crystals, researchers drilled into and removed fluid from a tiny inclusion (less than 10 ml). The fluid was inoculated into a growth medium under carefully controlled conditions. The bacteria that grew from these spores was characterized and the complete gene sequences of the 16S ribosomal DNA subsequently showed that the organism is related to present-day species as part of the lineage of Bacillus marismortui . Vreeland RH, Rosenzweig WD, Powers DW. 2000. Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal. Nature. 407:897-900.
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From this lecture, Know this Bacteria have structures that allow them to compete for nutrients Bacteria that move via flagella – swim. Swimming bacteria have sensory mechanisms that allow taxis (eg chemotaxis, phototaxis, magnetotaxis) Pure cultures are necessary for phenotypic characterization of microbes Streak plate is a technique that is used to isolate pure cultures from mixed cultures that is dependent on the ability of one microbe to grow via asexual means (binary fission, budding) to form a characteristic colony Colonies are descendents of one bacterial cell. All cells in a colony are genetically identical Colony morhpology for various bacterial genera are distinct, thus analysis of colony morphology can be used for phenotypic characterization Bacteria grow according to a normal growth curve with phases: lag, log, stationary, death Bacterial growth = growth of a population of bacteria Bacterial growth is effected by nutrient availability, environmental conditions Growth in particular environments is characteristic of particular bacteria and analysis of growth in various conditions can be used for phenotypic characterization Various methods can be used to measure bacterial cell growth
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This note was uploaded on 02/28/2011 for the course BSCI 223 taught by Professor Stein during the Spring '08 term at Maryland.

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Lecture 6 growth - Vreeland RH, Rosenzweig WD, Powers DW....

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