Molecular genetics and evolutionary relationship of PCB-degrading bacteria

Biphenyl-utilizing soil bacteria are ubiquitously distributed in the natural environment. They cometabolize a variety of polychlorinated biphenyl (PCB) congeners to chlorobenzoic acids through a 2,3-dioxygenase pathway, or alternatively through a 3,4-dioxygenase system. Thebph genes coding for the metabolism of biphenyl have been cloned from several pseudomonads. The biochemistry and molecular genetics of PCB degradation are reviewed and discussed from the viewpoint of an evolutionary relationship.Abbreviations BP biphenyl - bph BP/PCB-degradative gene - 23DHBP 2,3-dihydroxybiphenyl - HPDA 2-hydroxy-6-oxo-6-phenylhexa 2,4-dienoic acid - KF707 P. pseudoalcaligenes strain KF707 - LB400 Pseudomonas sp. strain LB400 - PCB polychlorinated biphenyls - Q1 P. paucimobilis strain Q1tod; toluene catabolic gene     

Some cultural and physiological aspects of methane-utilizing bacteria

A number of different methane-utilizing bacteria are described and compared with isolates of other investigators. The strains can be divided into three groups based on pigmentation, cell morphology and internal membrane structures. The oxidation of hydrocarbons, alcohols, aldehydes, fatty acids, methyl ethers and sugar phosphates by these bacteria was studied. There was much similarity between strains within the same group. Differences between groups as regards oxidative properties could be detected, but these were mainly quantitative and could not be used as taxonomical criteria. In addition, the inhibition of methane oxidation by metabolites and enzyme inhibitors was investigated. Formaldehyde proved to be the most active of the organic compounds tested. Iodoacetic acid inhibited both methane and methanol oxidation at concentrations of 0.03m or above. Of the inorganic compounds, KCN completely suppressed methane oxidation at 5×10^?4 m and to more than 90% at 5×10^?5 m.     

Erythrocyte deformability: physiological aspects

Analysis of published and author's data on the physiological role of deformability of erythrocytes, general mechanisms of modifications and disturbances, assessment methods, and the role of this blood feature for assessing the body status. This parameter is one of the most labile features of blood that shows highly sensitive reaction to practically any changes in metabolic process in erythrocytes and in a whole body. Degradation of deformability of erythrocytes under various types of oxygen deficit deteriorates functioning of the system of oxygen transportation at various levels: heart, vascular flow, oxygen-transporting blood function. Under hypoxia the parameters of oxygen-transporting blood function, of peroxide oxidation of lipids and of the antioxidation system correlate well with degradation of deformability of erythrocytes. Therefore, this parameter can be used an integrated criterion of disturbances in oxygen supply, and of prooxidation-antioxidation body status. Deformability of erythrocytes is a factor generating adequate the oxygen supply to tissue, and its degradation aggravates substitution of the oxidase pattern of oxygen utilization with the oxygenase pattern. This parameter is extremely important for the body functional status.     

Ceramide: physiological and pathophysiological aspects

Ceramide generated in the cell membrane has been shown to be central for the induction of apoptosis by death receptors and many stress stimuli such as gamma-irradiation, UV-light or infection with pathogens. Ceramide reorganizes cell membranes and forms large ceramide-enriched membrane domains that serve the spatial and temporal organization of the cellular signalosome upon activation. Thus, ceramide-enriched membrane domains mediate clustering of CD95 and DR5 to facilitate apoptosis, and they are also critically involved in apoptosis after irradiation, UV-light and infection with Pseudomonas aeruginosa. Since ceramide-enriched membrane domains amplify signals, their function is not restricted to the induction of apoptosis and it was shown that ceramide-enriched membrane domains are also involved in internalization of pathogens and the control of cytokine release from infected epithelial cells. Recent studies support the notion that changes of the ceramide metabolism are also critically involved in human diseases, for instance neurological disorders, cancer, infectious diseases and Wilson's disease.     

Neurosteroids: behavioral aspects and physiological implications]

The term "neurosteroids" applies to those steroids that are both formed in the nervous system from sterol precursors, and accumulate in the nervous system, at least in part, independently of peripheral steroidogenic glands secretion. Neurosteroids that are active on the central nervous system include, mainly, pregnenolone (PREG), dehydroepiandrosterone (DHEA) and their sulfate esters (PREG-S and DHEA-S), as well as the reduced metabolite of progesterone, 3 alpha,5 alpha-TH PROG also called allopregnanolone. These neuroactive neurosteroids alter neuronal excitability by modulating the activity of several neurotransmitter receptors and thus can influence behavior. PREG-S decreases the sleeping time in rats anesthetized with a barbiturate, which is consistent with its antagonist action on the GABAA receptor (GABAA-R). Allopregnanolone is anxiolytic in rats tested in a conflict paradigm, through an interaction at a site specific for the benzodiazepine (BZ) receptor inverse agonist RO15-4513 and/or at the picrotoxinin site on GABAA-R. The contribution of the amygdala, a key region involved in the control of anxiety, is also demonstrated for the anxiolytic action of allopregnanolone. An anti-agressive effect of DHEA can be observed in castrated male mice who become agressive in the presence of lactating females. This inhibition of agressiveness by DHEA is associated to a selective decrease in the brain of PREG-S, which may, in turn, trigger an increase of endogenous GABAergic tone. Finally, cognitive performances of aged rats tested in the Morris water maze and the Y-maze can be correlated with individual concentrations of PREG-S in the hippocampus, i.e. poor performance in both tasks with low levels of PREG-S. Remarkably, the memory deficits are significantly improved, albeit transiently, by an intra-hippocampal injection of PREG-S in impaired aged rats. Promnesiant PREG-S may then reinforce some neurotransmitter systems that can decline with age. This brief review provides evidence of the pharmacology and physiological correlates of neurosteroids involved in behavioral phenomena. However, neurobiological mechanisms of behavioral effects of neurosteroids await further investigation.     

The physiological genetics of denitrifying bacteria

The genetics of denitrification is a relatively unexplored area that has great promise. Species of Pseudomonas are probably best suited for study because they are widely found among natural denitrifying populations and are quite readily amenable to genetic analysis. The techniques for mutagenesis and for the exchange of chromosomal genes to characterize mutant strains have been well-developed in P. aeruginosa and are being developed in P. stutzeri. Mutants defective in the denitrification of nitrate, nitrite, and nitrous oxide are now available and will aid in describing the catalytic and regulatory elements of the denitrification pathway.     

The physiological genetics of denitrifying bacteria

The genetics of denitrification is a relatively unexplored area that has great promise. Species of Pseudomonas are probably best suited for study because they are widely found among natural denitrifying populations and are quite readily amenable to genetic analysis. The techniques for mutagenesis and for the exchange of chromosomal genes to characterize mutant strains have been well-developed in P. aeruginosa and are being developed in P. stutzeri. Mutants defective in the denitrification of nitrate, nitrite, and nitrous oxide are now available and will aid in describing the catalytic and regulatory elements of the denitrification pathway.     

Calcium balance in crustaceans: nutritional aspects of physiological regulation

Calcium homeostasis in crustaceans is influenced by their natural molting cycle that periodically requires replacement of the calcified exoskeleton in order for growth to occur. Whole body Ca balance transitions from intermolt (zero net flux) to premolt (net efflux) and postmolt (net influx at the rate of 2 mmol kg(-1)h(-1)). As such, molting provides a convenient model to study up- and down-regulation of epithelial Ca transporting proteins (such as Ca pumps and exchangers), the genes that encode them, and the steroid hormone (ecdysone) that putatively regulates the genes. Species residing in either freshwater or in terrestrial environments are more limited in their Ca availability than are marine species. Further the advance towards terrestriality is accompanied by decreased reliance upon branchial Ca uptake and increased reliance upon digestive uptake. This review will correlate Ca handling strategies with environment in semi-terrestrial and terrestrial crabs through examining environmental sources of Ca uptake. Ca homeostasis will also be discussed at the whole animal level, cellular, subcellular and molecular levels of regulation.     

Biochemical and physiological aspects of ubiquinone function

The brief review presents evidence that, in addition to the well-known functions of ubiquinone (coenzyme Q) as a component of the mitochondrial respiratory chain, this compound in the reduced form (ubiquinol) functions as an antioxidant. Ubiquinone in a partially reduced form is found in all cell membranes. It protects efficiently not only membrane phospholipids from peroxidation but also mitochondrial DNA and membrane proteins from free-radical-induced oxidative damage. This protective role of ubiquinol is independent of the effect of exogenous antioxidants, such as vitamin E, and it can both prevent the formation of free lipid radicals and eliminate them either directly or by regenerating vitamin E.     

Antizyme inhibitor 2: molecular, cellular and physiological aspects

Polyamines are small organic polycations essential for cell proliferation and survival. Antizymes (AZs) are small proteins regulated by polyamines that inhibit polyamine biosynthesis and uptake in mammalian cells. In addition, antizyme functions are also regulated by antizyme inhibitors, homologue proteins of ornithine decarboxylase lacking enzymatic activity. There are two antizyme inhibitors (AZIN), known as AZIN1 and AZIN2, that bind to AZs and negate their effects on polyamine metabolism. Here, we review different molecular and cellular properties of the novel AZIN2 with particular emphasis on the role that this protein may have in brain and testis physiology. Whereas AZIN1 is ubiquitously found in mammalian tissues, AZIN2 expression appears to be restricted to brain and testis. In transfected cells, AZIN2 is mainly located in the endoplasmic reticulum–Golgi intermediate compartment and in the cis-Golgi network. AZIN2 is a labile protein that is degraded by the proteasome by a ubiquitin-dependent mechanism. Regarding its physiological role, spatial and temporal analyses of AZIN2 expression in the mouse testis suggest that this protein may have a role in spermiogenesis.