Learning the language of bacteria.

Bacteria "talk" with each other by using small molecules that enable individuals in a population to coordinate their behavior. This language is termed quorum sensing. Bacterial pathogens may use this language to decide when to attack a host organism; therefore, the development of artificial signals to interfere with this signal process has become an area of intense chemical research.     

The bacteria of the sulphur cycle

This paper concentrates on the bacteria involved in the reductions and oxidations of inorganic sulphur compounds under anaerobic conditions. The genera of the dissimilatory sulphate-reducing bacteria known today are discussed with respect to their different capacities to decompose and oxidize various products of fermentative degradations of organic matter. The utilization of molecular hydrogen and formate by sulphate reducers shifts fermentations towards the energetically more favourable formation of acetate. Since acetate amounts to about two-thirds of the degradation products of organic matter, the complete anaerobic oxidation of acetate by several genera of the sulphate-reducing bacteria is an important function for terminal oxidation in sulphate-sufficient environments. The results of pure culture studies agree well with ecological investigations of several authors who showed the significance of sulphate reduction for the complete oxidation of organic matter in anaerobic marine habitats. In the dissimilatory sulphur-reducing bacteria of the genus Desulfuromonas the oxidation of acetate is linked to the reduction of elemental sulphur. Major characteristics of the anaerobic, sulphide-oxidizing phototrophic green and purple sulphur bacteria as well as of some facultative anoxygenic cyanobacteria, are given. By the formation of elemental sulphur and sulphate, these bacteria establish sulphur cycles with the sulphide-forming bacteria. In view of the morphological diversity of the sulphate-reducing bacteria and question of possible evolutionary relations to phototrophic sulphur bacteria is raised.     

The inorganic ion content of native aquatic bacteria.

In this study we have quantified the ionic content and volume of native aquatic, and two cultured bacteria, by X-ray microanalysis (XRMA) in the transmission electron microscope (TEM). The cellular concentrations of magnesium (means of 630 and 710 mM) were more than an order of a magnitude higher than the outside concentrations. The internal concentrations of sodium were on average 50-180 mM, and the [K+]/[Na+] ratios were in the range of 0.1-0.5; lowest for apparently nonactive bacteria. Magnesium and chloride probably act as the major components of cell turgor, since no other inorganic ions were present in comparable amounts. Our carbon and nitrogen measurements indicated that organic solutes are not likely to be present at significant concentrations. The estimated charge of inorganic ions (Na, Mg, P, Cl, K, and Ca) gave a positive net internal charge for most cells. However, in cultures of Vibrio natriegens, the high internal chloride concentration made the net inorganic charge negative in these cells. Our results suggest that growing marine bacterioplankton have an internal environment in which magnesium is the dominating cation. These results suggest that actively growing marine bacteria are physiologically adapted to high internal concentrations of both magnesium and chloride.