Bacteria

About: Bacteria is a research topic. Over the lifetime, 23676 publications have been published within this topic receiving 715990 citations. The topic is also known as: eubacteria.

Recovery and Enumeration of Viable Bacteria

Abstract: One of the greatest challenges facing soil microbiologists for more than a century has been the recovery and enumeration of "total" bacterial populations in soils. The difficulties lie not in the actual methodologies (the procedures are in fact relatively simple), but in the interpretation of results that is confounded by numerous errors arising chiefly from the nature of the substratum-the soil and the microbes themselves. It is safe to say that the dilution plate counting technique for the enumeration of microorganisms is one of the oldest and most widely used techniques in microbiology. The development of the procedures dates back to the period of Robert Koch and contemporaries (about 1880) when these pioneering microbiologists were faced with the problem of developing techniques for the cultivation of bacteria on "solid" culture media. Their efforts were directed mainly at characterizing microorganisms from a wide variety of habitats at a period when the field of microbiology (bacteriology in particular) was in its infancy. One of the earliest and lasting breakthroughs in the study of bacteria was the discovery of agar (a polysaccharide derived from marine algae) as a jelling agent for culture media. A unique and microbiologically useful property of agar is that it melts at 100°C but does not gel until cooled to about 40 °C making it suitable for incorporating live organisms in the gel. It is also resistant to decomposition by most terrestrial microorganisms making it well suited for use as a jelling agent for studies of soil microorganisms. Shortly after Koch's demonstrations of the plate culture technique (which actually employed flat glass plates) Petri (1887; see translation in Brock, 1961) described the use of dishes with loose-fitting overlapping lids (the well-known petri plate or dish prevalent in all microbiology labs) for the long-term growth of microorganisms with minimal contamination from external sources. Thus, with these pioneering innovations, the foundation for the cultivation and enumeration of microorganisms by the so-called dilution plate method was laid.

Ubiquinone and vitamin K in bacteria

Abstract: 3. Liver mitochondria isolated after suspension in 5 mM-sodium salicylate in 0-44m-sucrose carried out oxidative phosphorylation nearly as efficiently as the controls. 4. Salicylate was taken up by mitochondria at 00, but the binding was extremely labile. From 78 to 95 % of the salicylate taken up was removed by one rapid wash in sucrose medium. 5. The intracellular fluid of the livers of sailcylate-poisoned rats contained concentrations of salicylate from 0-8 to 4 0 mm. These concentrations approximate to the concentrations of salicylate in the plasma of these animals. 6. The presence of salicylate in the intracellular fluid of the livers of rats poisoned with salicylate in vivo is compatible with a physiological uncoupling effect of salicylate on mitochondria in vivo. Uncoupling cannot be demonstrated in mitochondria isolated from intoxicated rats because the salicylate is washed out during the isolation procedure.

Significance of bacteriophages for controlling bacterioplankton growth in a mesotrophic lake.

Abstract: Bacterium-specific viruses have attracted much interest in aquatic microbial ecology because they have been shown to be about 10 times more abundant than planktonic bacteria. So far most of the studies of interactions of planktonic bacteria and viruses have been done in marine environments, and very little is known about these interactions in lakes. Therefore, we studied phage proliferation in Lake Constance, a large mesotrophic lake in Germany. We enumerated bacteria and quantified the fraction of bacteria with mature intracellular phage particles and the number of free viruses by transmission electron microscopy. Between the end of March and early August 1992, peaks of bacterial abundance were followed in 1 to 2 weeks by peaks in the fraction of bacteria containing visible phage particles (0 to 1.7%) and in the number of free viruses (1 x 10(sup7) to 4 x 10(sup7) ml(sup-1)). We estimated that 1 to 17% +/- 12% of all bacteria were phage infected, implying that phage-induced mortality was