Visualization of bacterial microcolonies(bacterial cells appear as greenish-yellow dots)on the surface of soil particles by use of the fluorescent antibody technique. Cells are about 1 um in diameter
Visualization of bacterial microcolonies (bacterial cells appear as greenish-yellow dots) on the surface of soil particles by use of the fluorescent antibody technique. Cells are about 1 μm in diameter
Microbial activity Measurements Radioisotopes and microelectrodes Radioisotopes are very useful in measuring specific microbial processes at high sensitivity and also in obtaining information on the turnover rates of chemical species in nature Microbial ecologists have used small glass electrodes, referred to as microelectrodes, to study the activity of microorganisms in their microenvironments
Microbial Activity Measurements: Radioisotopes and Microelectrodes • Radioisotopes are very useful in measuring specific microbial processes at high sensitivity and also in obtaining information on the turnover rates of chemical species in nature. • Microbial ecologists have used small glass electrodes, referred to as microelectrodes, to study the activity of microorganisms in their microenvironments
Photosynthesis Use of radioisotopes to Light 14CO2 measure microbia rporate activity in nature Dark (a) photosynthesis measured in natural Sulfate reduction in mud seawater with 14c02 H2 present H35S (b) Sulfate reduction in mud measured with 35SO4 H≥ absent () Time (c)Methanogenesis Methanogenesis in mud measured in mud with 14CH. COO acetate labeled in either 14cH4 the methyl(CH3 c00-) or the carboxyl CH14CO0 Time (CH3 4C00-)carbon
Use of radioisotopes to measure microbial activity in nature. (a) Photosynthesis measured in natural seawater with 14CO2 (b) Sulfate reduction in mud measured with 35SO4 2- (c) Methanogenesis measured in mud with acetate labeled in either the methyl (14CH3COO- ) or the carboxyl (CH3 14COO- ) carbon
Platinum Microelectrodes (a) Schematic drawing of an Oxygen Glass microelectrode (b)Photo of microelectrodes being used in a microbial mat Gold 5 um (b)
Microelectrodes. (a) Schematic drawing of an oxygen microelectrode. (b) Photo of microelectrodes being used in a microbial mat
Microbial Activity Measurements: Stable Isotopes Enzyme substrates Enzyme that Fixed carbon fixes Co 12 Figure 14 13 Mechanism of isotopic fractionation using car- bon as an example. Although the ratio of natural abundance of 12CO, to 13CO2 is about 19: 1, enzymes that fix CO2 prefer entially fix the lighter isotope(12C). This results in fixed car bon being enriched in 12C and depleted in 13C relative to the starting substrate. The degree of 1C depletion is calculated as an isotopic fractionation (see legend to Figure 14.14 for calculation)
Microbial Activity Measurements: Stable Isotopes