Stationary phase mutagenesis: mechanisms that accelerate adaptation of microbial populations under environmental stress

Microorganisms are exposed to constantly changing environmental conditions. In a growth-restricting environment (e.g. during starvation), mutants arise that are able to take over the population by a process known as stationary phase mutation. Genetic adaptation of a microbial population under environmental stress involves mechanisms that lead to an elevated mutation rate. Under stressful conditions, DNA synthesis may become more erroneous because of the induction of error-prone DNA polymerases, resulting in a situation in which DNA repair systems are unable to cope with increasing amounts of DNA lesions. Transposition may also increase genetic variation. One may ask whether the rate of mutation under stressful conditions is elevated as a result of malfunctioning of systems responsible for accuracy or are there specific mechanisms that regulate the rate of mutations under stress. Evidence for the presence of mutagenic pathways that have probably been evolved to control the mutation rate in a cell will be discussed.     

Overexpression of plant uncoupling mitochondrial protein in transgenic tobacco increases tolerance to oxidative stress

An Arabidopsis thaliana cDNA clone encoding a plant uncoupling mitochondrial protein (AtPUMP1) was overexpressed in transgenic tobacco plants. Analysis of the AtPUMP1 mRNA content in the transgenic lines, determined by Northernblot, revealed variable levels of transgene expression. Antibody probing ofWestern blots of mitochondrial proteins from three independent transgenic lines showed significant accumulation of AtPUMP1 in this organelle. Overproduction of AtPUMP1 in transgenic tobacco plants led to a significantincrease in tolerance to oxidative stress promoted by exogenous hydrogen peroxide as compared to wild-type control plants. These results provide thefirst biological evidence for a role of PUMP in protection of plant cells against oxidative stress damage.     

Genotyping Yersinia pestis strains from various natural foci

Seven genetic variants of Yersinia pestis were detected by finger-printing of 85 strains of this bacterium from natural foci by means of a BX probe. Variants of Y. pestis strains correlate with certain species of carriers.     

Phylogeny of Marine Bacillus Isolates from the Gulf of Mexico

The phylogeny of 11 pigmented, aerobic, spore-forming isolates from marine sources was studied. Forty-two biochemical characteristics were examined, and a 16S rDNA sequence was obtained for each isolate. In a phylogenetic tree based on 16S sequencing, four isolates (NRRL B-14850, NRRL B-14904, NRRL B-14907, and NRRL B-14908) clustered with B. subtilis and related organisms; NRRL B-14907 was closely related to B. amyloliquefaciens. NRRL B-14907 and NRRL B-14908 were phenotypically similar to B. amyloliquefaciens and B. pumilus, respectively. Three strains (NRRL B-14906, NRRL B-14910, and NRRL B-14911) clustered in a clade that included B. firmus, B. lentus, and B. megaterium. NRRL B-14910 was closely related phenotypically and phylogenetically to B. megaterium. NRRL B-14905 clustered with the mesophilic round spore-producing species, B. fusiformis and B. sphaericus; the isolate was more closely related to B. fusiformis. NRRL B-14905 displayed characteristics typical of the B. sphaericus-like organisms. NRRL B-14909 and NRRL B-14912 clustered with the Paenibacillus species and displayed characteristics typical of the genus. Only NRRL B-14851, an unusually thin rod that forms very small spores, may represent a new Bacillus species. Received: 8 December 1999 / Accepted: 14 February 2000     

Neuroscience at the end of the 2nd millennium: a shift in paradigms

The new neuroscience data rapidly accumulating by the end of the second millennium calls for radical revision of many long-established and widely accepted postulates. This paper reviews some data leading to new concepts of life and work of neurons. The adult brain contains stem cells which are the source of the precursors for all main types of the brain cells: neurons, astrocytes, and oligodendroglia. These cells can substitute the deteriorating elements in the adult and even old brain. The neurons occur to be highly resistant to lesion of their processes as well to anoxia, and inhibitory neurons are shown to be especially stable in some pathological conditions. Changes in the afferent inputs result in various types of rapid compensatory morphological and functional reorganizations at different levels. Thus, the previous fatalistic view of the nervous system is substituted now for an optimistic one regarding various possibilities of prolongation and restoration of normal functioning of the brain. Simultaneously, our concepts of the neurons changed drastically. An unitary neuron may operate by several neurotransmitting substances; their synaptic influences upon the dendrites may evoke the active propagation of calcium and sodium spikes, their axons may differentially release transmitter substances depending on parameters of excitation. All neuronal functions are helped and controlled by astroglia, which participates in the synthesis of transmitters and protects the neurons from the excitotoxic death. Besides the synaptic interactions between the neurons, there exist other types of communications, such as volume conduction of transmitters after their spillover from the excited synapses and non-synaptic (varicose) zones, as well as exchange of molecules and ions through the gap junctions. A complex picture of interneuronal communications with multiple synaptic, presynaptic, and parasynaptic interactions is further complicated by the intimate participation of neurotrophic substances and "mediators of the immune system"--cytokines in these processes. The mutual regulatory influences between neurotransmitters, neurotrophic, and neuroimmune systems show that in normal conditions all they are working in concert. This increase in number of factors determining the final result of interaction between the neurons contributes new difficulties to the development of theoretical concepts or simulation of brain functions. In this context it is possible to speak about a certain crisis of theoretical neurobiology at present, because multiplicity of fine details obtained by molecular neurobiology and neurogenetics cannot be integrated in a coherent view of the brain functions. Overcoming the present gap between the analytic and synthetic approaches to understanding the brain work will be the main aim for the neurobiologists of the third millennium.     

Comparative analysis of the learning ability in Morris water test in rats with the various rate of active acquisition of the avoidance conditioned reflex

Place learning in Morris place navigation task was studied in male rats of KHA (Koltushi High Avoidance) and KLA (Koltushi Low Avoidance) rat strains. These strains were selected for different rate of acquisition of active avoidance in a shuttle box. At the initial stages of learning and after changing the experimental conditions, the performance of KLA rats was significantly better than that of KHA. Analysis of individual escape latency showed that the latency of the platform finding in the first trial had a significant effect on successful performance in the second trial. This effect was different in KHA and KLA rats. As distinct from KLA, the KHA rats demonstrated more rigid strategy in spatial orientation, the clear-cut thigmotropism was characteristic for their behavior in water.     

Public Reform and the Privatisation of Poverty: Some Institutional Determinants of Health Seeking Behaviour in Southern Tanzania

This paper explores the changing institutional context of health servicedelivery in rural Tanzania through an anthropological analysis of thekinds of healing strategies pursued by men and women when they are ill.In some rural districts popular dissatisfaction with state medicalprovision is not manifested in a rejection of the allopathic medicinewith which it is associated, but in increased reliance on an emerginginformal sector of private medical provision. Although this sectorprovides a valued and accessible service to certain categories ofclients it delivers poor quality treatment, serving to reinforce thecyclical relationship between poverty and ill health. Despite the bestintentions of major public sector reforms neither government nor otheragencies are able to meet rural demand for health services. Reliance onthe parallel market for medical provision is likely to continue, atleast in the short term, with negative consequences for health.