Methods in Microbial Ecology Lecture 16 Feb 27, 2006 The study of how microorganisms interact with each other and with their environment. Biodiversity – isolation, identification and quantification of microorganisms in their native habitats
The study of how microorganisms interact with each other and with their environment.
In nature, microorganisms exist in mixed cultures called microbial communities
A miniature anoxic ecosystem that is used as a long-term inoculant source for enrichment cultures
supplementing with a compound that it can degrade
Dominant organism in an enrichment culture does not necessarily represent the dominant organism in a natural habitat.
Dilution of a mixed culture in tubes containing molten agar. Individual colonies become separated and embedded in the agar
MPN in this example is 105 – 106 recoverable cells per gram of sample
Cells in capillary tubes can be optically trapped, isolated. Tube is broken and the cell is flushed out into sterile medium to initiate a pure culture
Methods of fluorescent staining that distinguish between living and dead cells. Example: LIVE/DEAD Bac Light
Exploits the specificity of antibodies to recognize a particular cell-surface protein of an organism
Detection of Sulfobolus acidocaldarius on the surface of soil particles
Fluoresent in situ hybridization uses fluorescently-labelled single-stranded DNA or RNA probes to bind directly to its complementary sequence in a nucleic acid.
FISH technology used to detect the presence of specific genes in a sample. Example – is a nitrogen-fixing organism present? Look for nitrogenase
Used to determine whether a given gene is being expressed in a sample at a particular time
The most abundant members of a microbial community may never have been seen in laboratory culture
Controls such as the ‘killed cell control’ guarantee that transformation
of a radiolabeled compound is due to a microbial rather than a strictly
Tiny glass electrodes (2-100 m diameter) to measure pH, oxygen, carbon dioxide, hydrogen, hydrogen sulfide. Often used to measure chemical reactions in microbial mats:
Isotopes that are not radioactive. Carbon and sulfur are the most commonly used in microbiology