Aerobic methylotroph bacteria as phytosymbionts]

This paper deals with the physiological, biochemical, and molecular genetic aspects of the interaction of aerobic methylotrophic bacteria with plants by means of phytohormones (such as cytokinins and auxins) and other physiologically active substances (vitamins, exopolysaccharides, bioprotectants). The state of the art and the prospects of research in the field of bacteria-plant interactions and the application of aerobic methylotrophs in plant biotechnology is discussed.     

Moderately haloalkaliphilic aerobic methylobacteria

Aerobic methylobacteria utilizing oxidized and substituted methane derivatives as carbon and energy sources are widespread in nature and involved in the global carbon cycle, being a unique biofilter on the path of these C1 compounds from different ecosystems to the atmosphere. New data on the biological features of moderately halophilic, neutrophilic, and alkaliphilic methylobacteria isolated from biotopes with higher osmolarity (seas, saline and soda lakes, saline soils, and deteriorating marble) are reviewed. Particular attention is paid to the latest advances in the study of the mechanisms of osmoadaptation of aerobic moderately haloalkaliphilic methylobacteria: formation of osmolytes, in particular, molecular and genetic aspects of biosynthesis of the universal bioprotectant ectoine. The prospects for further studies of the physiological and biochemical principles of haloalkalophily and for the application of haloalkaliphilic aerobic methylobacteria in biosynthesis and biodegradation are discussed.     

Changes of chlorine isotope composition characterize bacterial dehalogenation of dichloromethane

Fractionation of dichloromethane (DCM) molecules with different chlorine isotopes by aerobic methylobacteria Methylobacterium dichloromethanicum DM4 and Albibacter nethylovorans DM10; cell-free extract of strain DM4; and transconjugant Methylobacterium evtorquens Al1/pME 8220, expressing the dcmA gene for DCM dehalogenase but unable to grow on DCM, was studied. Kinetic indices of DCM isotopomers for chlorine during bacterial dehalogenation and diffusion were compared. A two-step model is proposed, which suggests diffusional DCM transport to bacterial cells.     

Hansschlegelia plantiphila gen. nov. sp. nov., a new aerobic restricted facultative methylotrophic bacterium associated with plants

A new genus, Hansschlegelia, and a new species, Hansschlegelia plantiphila, are proposed for three strains of methanol-utilizing bacteria isolated from lilac buds (strain S(1)(T)), linden buds (strain S(2)) and blue spruce needles (strain S(4)), which were selected in winter at -17 degrees C. These bacteria are aerobic, Gram-negative, colorless, non-motile short rods that multiply by binary fission and employ the ribulose bisphosphate (RuBP) and the serine pathways for C(1) assimilation. The strains have a limited number of growth substrates and use methanol, methylamine, formate, CO(2)/H(2) and glycerol as carbon and energy sources. Only strain S(1)(T) grows with ethanol and inulin. The strains are neutrophilic and mesophilic, and synthesize phytohormones (auxins and cytokinins) and vitamin B(12). Their major cellular fatty acids are saturated C(16:0), straight-chain, unsaturated C(18:1)(omega)(7) and cyclopropane C(19 cyc) acids. The main ubiquinone is ubiquinone-10 (Q-10). The dominant phospholipids are phosphatidylethanolamine, phosphatidylcholine and diphosphatidylglycerol (cardiolipin). The DNA G+C content is 68.5+/-0.2 mol%. The strains share almost identical 16S rRNA gene sequences, a high DNA-DNA hybridization value (72-86%) and represent a novel lineage of autotrophic methanol-utilizing bacteria within the Alphaproteobacteria. Collectively, these strains comprise a new genus and species H. plantiphila gen. nov., sp. nov., with strain S(1)(T) (VKM B-2347(T), NCIMB 14035(T)) as the type strain.     

Cerebral hemodynamic reaction to physical exercise of moderate intensity

The aim of this research was to study the cerebral hemodynamic reaction to stepped increase of physical exercises during the bicycle ergometer test in 12 young healthy male patients. The starting value of exercise was 0.25 W/kg of the body weight, with the 0.25 W/kg increase at every subsequent step up to the value of 1.75 W/kg of the body weight. Hemodynamic parameters were registered with the Doppler ultrasonography of middle cerebral artery before the study, during the last 10 seconds of every step, and during the 3 minutes of restorative period with a 1-minute interval. The peak systolic blood flow increase in the middle cerebral artery was observed only as the result of low intensity exercises (0.25 W/kg of the body weight). The blood pressure (BP) restoration occurred by the end of the third minute of the rest, while the cerebral hemodynamic indices became normal during the first minute. The research revealed a correlation between increases of vascular resistance caused by physical exercises and the BP, and no correlation between increases of peak systolic blood flow and BP, which displays the phenomenon of cerebral circulation autoregulation.     

Adaptation of aerobic methylobacteria to dichloromethane degradation

A shortening of the lag phase in dichloromethane (DCM) consumption was observed in the methylobacteria Methylopila helvetica DM6 and Albibacter methylovorans DM10 after prior growth on methanol with the presence of 1.5% NaCl. Neither heat nor acid stress accelerated methylobacterium adaptation to DCM consumption. Sodium azide (1 mM) and potassium cyanide (1 mM) inhibited consumption of DCM by these degraders but not by transconjugants Methylobacterium extorquens AM1, expressing DCM dehalogenase but unable to grow on DCM. This indicates that the degrader strains possess energy-dependent systems of transport of DCM or chloride anions produced during DCM dehalogenation. Inducible proteins were found in the membrane fraction of A. methylovorans DM10 cells adapted to DCM and elevated NaCl concentration.     

System of oligonucleotide primers for detection and amplification of the emoA gene encoding bacterial ethylenediaminetetraacetate monooxygenase

A system of primers was designed on the basis of analysis of nucleotide sequences of the emoAgene encoding ethylenediaminetetraacetate (EDTA) monooxygenase, which are deposited in GenBank. This system of primers makes it possible to obtain emoA gene fragments approximately 750 bp long for bacterial destructors of EDTA. Polymerase chain reaction (PCR) of total DNA isolated from enrichment and pure cultures showed that this system can be effectively used for detecting the emoAgene in representatives of Alpha- and Gammaproteobacteria. Partial sequences of emoA genes of bacteria of the genera Chelativorans and Stenotrophomonas, which are able to degrade this pollutant, have been sequenced and deposited in GenBank.     

Growth of Methylosinus trichosporium OB3b on methane and poly-beta-hydroxybutyrate biosynthesis

Optimal conditions for batch cultivation of the obligate methanotroph Methylosinus trichosporium OB3b on methane without superatmospheric pressure were chosen. The yield of absolutely dry biomass after 120 h of growth reached 20 g/l. This biomass contained 30% poly-beta-hydroxybutyrate (PHB) with molecular weight 300 kDa. The growth process included the stages of biomass growth and PHB biosynthesis. The latter stage occurred under nitrogen-deficiency conditions. It was accompanied by an increase in the activity of PHB biosynthesis enzymes (beta-ketothiolase, acetoacetyl-CoA reductase, and PHB synthase) and the main NAD(P)H producer, methylenetetrahydromethanopterin dehydrogenase. The activity of PHB depolymerase increased insignificantly.     

Sequential colonization by river periphyton analysed by microscopy and molecular fingerprinting

1. An artificial glass substratum was incubated in the River Danube for a period of 28 days in order to detect the sequential colonization of microorganisms.
2. Light and fluorescent microscopy showed that microalgae and the picoalgal fraction on the slides increased rapidly over the first 2 weeks of colonization. Diatoms were numerically the most abundant component of the periphyton and their species richness and diversity increased rapidly in the early phase of colonization whereas diversity subsequently increased moderately.
3. Evenness of the diatom community was initially high, lower in the intermediate phase and again higher later on. Succession involving early, intermediate and late colonizer species was observed. Community composition during the first 5 days of colonization was very different from later stages whereas there were only minor changes subsequently.
4. Molecular community analysis by means of terminal restriction fragment length polymorphism analysis of PCR amplified 16S rRNA and 18S rRNA genes pointed to even larger differences between the composition of samples obtained early and late in the period.
5. The number of 18S rRNA and 16S rRNA terminal restriction fragments (T-RF-s) was variable over the colonization period and the fragment patterns of both the bacterial and eukaryotic portion of the microbial community were variable, with most T-RF-s unique to a single sample, suggesting a wide diversity and dynamic properties of periphytic organisms.