Showing papers in "Advances in Microbial Physiology in 1988"

Physiology of lipoteichoic acids in bacteria.

Abstract: Publisher Summary The widespread occurrence of lipoteichoic acids and their assumed structural homogeneity, together with their singular location on the bacterial membrane, led to the hypothesis that they may play an essential part in the cell physiology of Gram-positive bacteria. In the meantime, deviant lipoteichoic acid structures have been detected and, more importantly, glycosyl and alanyl substituents have been found to affect considerably the biological activities of the classical poly (g1ycerophosphate) lipoteichoic acids. Mutants defective in lipoteichoic acid biosynthesis have not yet been described. However, loss of rather substantial fractions of cellular lipoteichoic acid, caused for example by phosphate limitation, osmotic shock, or treatment with penicillin can apparently be tolerated by certain bacteria without significantly affecting the ability of lipoteichoic acid-depleted cells to survive. This does not preclude that a minor fraction of lipoteichoic acid may be indispensable or, that its presence may provide selective advantages to the organism.

The physiology and biochemistry of pili.

Abstract: Publisher Summary This chapter reviews and discusses the structure and function of pili in light of recent advances employing biochemical, immunological, and genetic approaches Bacterial “fimbriae” or “pili” are thin (2-1 2 nm diameter) non-flagellar protein filaments found on the surfaces of many types of bacteria The adhesive properties of pili allow them to bind to other bacteria, bacteriophages, mammalian cells, and inert surfaces The chapter discusses the classification scheme for pili based on morphology, function, and biochemical properties It describes three major groups of pilus—namely, conjugative, adhesive, and N-methylphenylalanine (NMePhe) pili The simplest classification of pili on the basis of function is the division into two broad groups: “conjugative” and “adhesive” pili It is noted that the biochemical properties help to identify the subpopulations of these pili The conjugative pili show variable preferences for promoting bacterial mating in liquid or on solid media Flexible pili generally confer the “universal mating type” and promote mating in liquid media and on solid surfaces equally well, whereas rigid pili are usually associated with “surface preferred” or “surface obligatory” mating types

Archaebacteria: the comparative enzymology of their central metabolic pathways

Abstract: Publisher Summary It is noted that for the purposes of establishing the phylogenetic status of the archaebacteria, much emphasis has been placed on the molecular biology of these organisms and on the chemical nature of their cell walls and membranes. However, it is also becoming clear that the pathways of metabolism in archaebacteria and their constituent enzymes are equally fruitful areas for investigation. This chapter focuses on the enzymology of archaebacteria, not in isolation but in comparison with that of eubacteria and eukaryotes. The enzymes of the central metabolic pathways have been reviewed because these pathways are thought to be some of the first cellularly established metabolic routes and are the most studied and well-characterized systems in non-archaebacterial species. Archaebacteria grow in extreme environments and therefore their macro- molecules will be structurally adapted to function under such conditions. Thermoacidophilic archaebacteria grow at temperatures between 55 and 110°C and in pH values as low as pH 1-2. Although there can be no temperature differential between the outside and inside of a cell, it is thought that cytoplasmic pH values are approximately neutral.

Carboxysomes and ribulose bisphosphate carboxylase/oxygenase.

Abstract: Publisher Summary This chapter focuses on recent advances made in the knowledge of the occurrence, composition, properties, and possible functions of carboxysomes. It also discusses the rapidly expanding field of research on Ribulose 1, 5-bisphosphate carboxylase/oxygenase (RuBisCO) enzymes. The chapter compares the RuBisCO enzymes of prokaryotes that contain carboxysomes with those that do not. Insight into carboxysome function also may be gained by comparison with other prokaryotic inclusions and with the compartmentation of RuBisCO in chloroplasts. The knowledge of carboxysome composition is necessary to provide an understanding of the functions of the organelles and their contribution to the physiology of the cell. The carboxysomes isolated from the different physiological groups of autotrophs are similar in the possession of two polypeptides that coincide in terms of molecular mass with the large (L) subunits and small (S) subunits of their respective RuBisCO enzymes. The use of carboxysomes as ecophysiological markers and the prospects of producing RuBisCO-containing inclusion bodies in recombinant micro-organisms is also discussed in the chapter.

Hydrogen metabolism in Rhizobium: energetics, regulation, enzymology and genetics

Abstract: Publisher Summary Hydrogen (H 2 ) utilization can occur in aerobic and anaerobic bacteria and is linked to ATP-producing electron transport systems. The aerobic N 2 -fixing bacteria evolve and consume H 2 , and among this group are the rhizobia, the azotobacter , and the cyanobacteria. Hydrogen evolution by these micro-organisms is catalyzed by nitrogenase and an uptake hydrogenase is responsible for H 2 oxidation. Whereas the cyanobacteria have hydrogenase activity even in cells not fixing N 2 , hydrogenase is generally derepressed under N 2 -fixing conditions in Azotobacter and in hydrogen uptake positive (Hup+) strains of Rhizobium . In addition, the autotrophic growth of R. japonicum on H 2 has been demonstrated in the laboratory, and thus H 2 oxidation by this bacterium, without concomitant N 2 fixation, may conceivably occur in nature under some conditions. This chapter discusses H 2 metabolism in Rhizohium, particularly R. japonicum and R. leguminosarum . The enzymology of hydrogenase concentrates on R. japonicum because the R. leguminosarum enzyme has yet to be purified and characterized. Different approaches have been taken in studying genetic problems concerning H 2 metabolism in R. japonicum and R. leguminosarum.