Physiological,biochemical, and cytological characteristics of a halotolerant and alkalitolerant methanotroph grown on methanol

The halotolerant alkaliphilic methanotroph Methylomicrobium buryatense 5B is capable of growth at high methanol concentrations (up to 1.75 M). At optimal values of pH and salinity (pH 9.5 and 0.75% NaCl), the maximum growth rate on 0.25 M methanol (0.2 h-1) was twice as high as on methane (0.1 h-1). The maximum growth rate increased with increasing medium salinity and was lower at neutral than at alkaline pH. The growth of the bacterium on methanol was accompanied by a reduction in the degree of development of intracytoplasmic membranes, the appearance of glycogen granules in cells, and the accumulation of formaldehyde, formate, and an extracellular glycoprotein at concentrations of 1.2 mM, 8 mM, and 2.63 g/l, respectively. The glycoprotein was found to contain 23% protein and 77% carbohydrates, the latter being dominated by glucose, mannose, and aminosugars. The major amino acids were glutamate, aspartate, glycine, valine, and isoleucine. The glycoprotein content rose to 5 g/l when the concentration of potassium nitrate in the medium was augmented tenfold. The activities of sucrose-6-phosphate synthase, glycogen synthase, and NADH dehydrogenase in methanol-grown cells were higher than in methane-grown cells. The data obtained suggest that the high methanol tolerance of M. buryatense 5B is due to the utilization of formaldehyde for the synthesis of sucrose, glycogen, and the glycoprotein and to the oxidation of excess reducing equivalents through the respiratory chain.     

Terminal oxidases in different genera of the family Microbacteriaceae

The nature of terminal oxidases in representatives of four different genera of the family Microbacteriaceae was studied. It was found that the late-logarithmic and early-stationary cells of all of the investigated strains of the genera Plantibacter and Okibacterium contain the aa3-type cytochrome oxidase. Bacteria of the genera Rathayibacter and Agreia synthesize three oxidases, the bb3- and aa3-type cytochrome oxidases and nonheme cyanide-resistant oxidase, in proportions dependent on the cultivation conditions and the growth phase. Oxygen deficiency in the cultivation medium induces the synthesis of the bd-type oxidase in all of the microorganisms studied. The data obtained provide evidence that the type of terminal oxidases, along with the known chemotaxonomic characteristics, may serve to differentiate the genera of the family Microbacteriaceae at the phenotypic level.     

Electron microscopic detection and in situ characterization of bacterial nanoforms in extreme biotopes

The morphology, ultrastructure, and quantity of bacterial nanoforms were studied in extreme biotopes: East Siberia permafrost soil (1-3 Ma old), petroleum-containing slimes (35 years old), and biofilms from subsurface oil pipelines. The morphology and ultrastructure of microbial cells in natural biotopes in situ were investigated by high-resolution transmission electron microscopy and various methods of sample preparation: ultrathin sectioning, cell replicas, and cryofractography. It was shown that the biotopes under study contained high numbers of bacterial nanoforms (29-43% of the total number of microorganisms) that could be assigned to ultramicrobacteria due to their size (diameter of < or =0.3 microm and volume of < or =0.014 microm3) and structural characteristics (the presence of the outer and cytoplasmic membranes, nucleoid, and cell wall, as well as their division patterns). Seven different morphostructural types of nanoforms of vegetative cells, as well as nanospores and cyst-like cells were described, potentially representing new species of ultramicrobacteria. In petroleum-containing slimes, a peculiar type of nanocells was discovered, gram-negative cells mostly 0.18-0.20 x 0.20-0.30 microm in size, forming spherical aggregates (microcolonies) of dividing cells in situ. The data obtained promoted the isolation of pure cultures of ultramicrobacteria from petroleum-containing slimes; they resembled the ultramicrobacterium observed in situ in their morphology and ultrastructure.     

Methylotrophic autotrophy in Beijerinckia mobilis

Representatives of the genus Beijerinckia are known as heterotrophic, dinitrogen-fixing bacteria which utilize a wide range of multicarbon compounds. Here we show that at least one of the currently known species of this genus, i.e., Beijerinckia mobilis, is also capable of methylotrophic metabolism coupled with the ribulose bisphosphate (RuBP) pathway of C1 assimilation. A complete suite of dehydrogenases commonly involved in the sequential oxidation of methanol via formaldehyde and formate to CO2 was detected in cell extracts of B. mobilis grown on CH3OH. Carbon dioxide produced by oxidation of methanol was further assimilated via the RuBP pathway as evidenced by reasonably high activities of phosphoribulokinase and ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO). Detection and partial sequence analysis of genes encoding the large subunits of methanol dehydrogenase (mxaF) and form I RubisCO (cbbL) provided genotypic evidence for methylotrophic autotrophy in B. mobilis.     

New thermophilic methanotrophs of the genus Methylocaldum

Two pure cultures of obligate methanotrophs, strains H-11 and 0-12, growing in the temperature range from 30 to 61 degrees C with an optimum at 55 degrees C were isolated from samples of silage and manure. Based on the results of analysis of the 16S rRNA genes, membrane-bound methane monooxygenase, and phenotypic properties, the isolates were assigned to the genus Methylocaldum. Significant temperature-dependent variations in morphology and phospholipid and fatty acid composition were revealed. Both strains assimilated methane carbon via the ribulose monophosphate, serine, and ribulose bisphosphate pathways. The activity of hexulose phosphate synthase was independent of the cultivation temperature; however, the activities of hydroxypyruvate reductase and ribulose bisphosphate carboxylase were higher in cells grown at 55 degrees C that in cells grown at 37 degrees C, indicating the important roles of the serine and ribulose bisphosphate pathways in the thermoadaptation of the strains under study. NH4+ assimilation occurred through reductive amination of alpha-ketoglutarate and via the glutamate cycle. The relationship between the physiological-biochemical peculiarities of the isolates and their thermophilic nature is discussed.     

Taxonomic characterization of new alkaliphilic and alkalitolerant methanotrophs from soda lakes of the Southeastern Transbaikal region and description of Methylomicrobium buryatense sp.nov

Five strains of obligate methanotrophic bacteria (4G, 5G, 6G, 7G and 5B) isolated from bottom sediments of Southeastern Transbaikal soda lakes (pH 9.5-10.5) are taxonomically described. These bacteria are aerobic, Gram-negative monotrichous rods having tightly packed cup-shaped structures on the outer cell wall surface (S-layers) and Type I intracytoplasmic membranes. All the isolates possess particulate methane monooxygenase (pMMO) and one strain (5G) also contains soluble methane monooxygenase (sMMO). They assimilate methane and methanol via the ribulose monophosphate pathway (RuMP). The isolates are alkalitolerant or facultatively alkaliphilic, able to grow at pH 10.5-11.0 and optimally at pH 8.5-9.5. These organisms are obligately dependent on the presence of sodium ions in the growth medium and tolerate up to 0.9-1.4 M NaCl or 1 M NaHCO3. Although being mesophilic, all the isolates are resistant to heating (80 degrees C, 20 min), freezing and drying. Their cellular fatty acids profiles primarily consist of C(16:1). The major phospholipids are phosphatidylethanolamine and phosphatidylglycerol. The main quinone is Q-8. The DNA G+C content ranges from 49.2-51.5 mol %. Comparative 16S rDNA sequencing showed that the newly isolated methanotrophs are related to membres of the Methylomicrobium genus. However, they differ from the known members of this genus by DNA-DNA relatedness. Based on pheno- and genotypic characteristics, we propose a new species of the genus Methylomicrobium Methylomicrobium buryatense sp. nov.     

Fluctuating asymmetry in bank vole populations (Rodentia, Arvicolinae) reflects stress caused by landscape fragmentation in the Mont-Saint-Michel Bay

In intensively farmed, reclaimed areas (polders) of Mont-St-Michel Bay, France, bank voles ( Clethrionomys glareolus ) live in fragmented hedgerows, where populations are small and dispersal rates and genetic diversity are low. These small populations are likely to have been exposed to potential environmental and/or genetic stress. The sensitivity of development to stress can be measured by fluctuating asymmetry (FA). FA was calculated for three samples from a disturbed area and one sample from an adjacent, more connected and undisturbed landscape. Size FA was estimated from 16 measurements of the skull and teeth whilst shape asymmetry was estimated from the skull alone. Bank voles in fragmented hedgerows of the disturbed area had a higher degree of FA than bank voles from the more extensive and more connected hedges of the undisturbed area. These results were confirmed by the study of shape asymmetry, body mass and centroid size of the skull. There were no differences in FA between the three disturbed area samples. We conclude that FA does not reveal differences in the development of bank voles living in isolation under different local conditions in the various parts of the disturbed area. However, FA may allow differentiation between populations from greatly contrasting landscapes.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 37–44.     

Halobacterium salinarum storage and rehydration after spray drying and optimization of the processes for preservation of carotenoids

Extremophiles - Spray drying is appropriate for the preservation of halophilic microorganisms due to the nature of these microorganisms, as they survive in adverse environmental conditions by being...     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.