A. M. Boronin

Growth promotion of blackcurrant softwood cuttings by recombinant strain Pseudomonas fluorescens BSP53a synthesizing an increased amount of indole-3-acetic acid

Two isogenic Pseudomonas ftuorescens strains differing in plant hormone production were used to inoculate softwood cuttings. Production of bacterial indole-3-acetic add (IAA) was shown to have a stimulatory effect on the root development of blackcurrant softwood cuttings, whereas for sour cherry it was inhibitory. The size of the population of the inoculated strain on the root surface of the cuttings correlated with the effect observed.

Degradation of petroleum hydrocarbons by facultative anaerobic bacteria under aerobic and anaerobic conditions

Abstract Nitrate-reducing bacterial strains ( Pseudomonas sp. BS2201, BS2203 and Brevibacillus sp. BS2202) isolated from petroleum-contaminated soil were capable of degrading petroleum hydrocarbons under aerobic and anaerobic conditions. Under aerobic conditions (a 10-day experiment in liquid media) the strains degraded 20–25% of the total extractable material (TEM), including up to 90–95% of all alkanes analyzed ( n -C 10 –C 35 ). Under anaerobic conditions (a 50-day experiment) these organisms degraded 15–18% of the TEM, 20–25% of some alkanes, and 15–18% of selected polycyclic aromatic hydrocarbons. The strains also degraded saturated hydrocarbons under anaerobic conditions in the absence of nitrates as electron acceptors.

Phenanthrene metabolism by Pseudomonas and Burkholderia strains

Abstract Five pseudomonads and two Burkholderia spp. capable of utilizing naphthalene or phenanthrene as a sole source of carbon and energy were isolated from oil-contaminated soils through enrichment cultures. All the strains studied contained large plasmids. In six strains, they were involved in biodegradation of specific substrates. The major intermediates of phenanthrene metabolism accumulated in the culture liquids were 1-hydroxy-2-naphthoate and 2-hydroxy-1-naphthoate. The strains studied differed in the accumulation pattern of these intermediates. 2-Naphthol, an oxidation product of 2-hydroxy-1-naphthoate, exerted a toxic effect on microorganisms. The phenanthrene-degrading activity of Pseudomonas strains depended on their ability to utilize 1-hydroxy-2-naphthoate. In the Pseudomonas strains under study, phenanthrene metabolism involved the enzymes of naphthalene degradation.

Diversity of Pseudomonas plasmids: To what extent?

Results obtained in studies of the biology of Pseudomonas plasmids are presented here as a mini-review. These data indicate that plasmids are ubiquitous in Pseudomonas, but the frequency of their occurrence varies greatly in particular species, or groups of species and in different microbial habitats. Some species of Pseudomonas, for instance P. aeruginosa, possess great diversity of plasmids both from the viewpoint of their incompatibility properties and their ability to endow bacteria with additional features such as resistance to antibiotics or heavy metals, degradation of xenobiotics or inhibition of phage development.

Evaluation of a Gluconobacter oxydans whole cell biosensor for amperometric detection of xylose

Abstract Whole cells of Gluconobacter oxydans were employed in a microbial sensor for xylose determinations using Clark-type electrodes. Bacterial cells were immobilized on chromatographic paper by simple physical adsorption and attached to the surface of the electrodes. The lower limit of xylose detection was approximately 0·5 mM and measurements were useful up to at least 20 mM xylose. Physiological buffers showed little effect on biosensor function. Responses were highly reproducible, showing a standard deviation of 6·7% over 10 consecutive measurements. Whole cell biosensors were relatively stable, retaining 60% of initial activity after 35 days of dry storage at 4°C. Xylose detection was not significantly affected by the presence of xylitol, suggesting that biosensors will be useful in monitoring conversions of these compounds. However, glucose or ethanol elicited a 10-fold higher response than xylose at equal concentrations (1 mM). Such interfering materials will need to be controlled or concurrently monitored in specific sensor applications.

FET-microbial sensor for xylose detection based on Gluconobacter oxydans cells

A potentiometric biosensor for xylose was devised utilizing Gluconobacter oxydans whole cells. Immobilization methods based on physical adsorption were used for G. oxydans cells and extracellular pH changes resulting from xylose dehydrogenation were monitored by a field effect transistor (FET). The G. oxydans, FET-based sensor detected xylose at a lower limit of 0.5 mM. From 5.0 to 30 mM xylose, the response of the sensor was linear. Expectedly, output signals were significantly suppressed by buffer (Tris-HCl). Responses were essentially stable for at least four weeks of storage and showed only a slight loss of initial xylose sensitivity. Xylitol exerted an insignificant influence on the sensors response to xylose. However, the response to glucose was 5 times higher in relation to that of xylose at the same concentration (1 mM). For xylose determinations in the presence of glucose, a two-step assay is discussed.

Modeling of lactic acid fermentation of leguminous plant juices

Lactic acid fermentation of leguminous plant juices was modeled to provide a comparative efficiency assessment of the previously selected strains of lactic acid bacteria as potential components of starter cultures. Juices of the legumes fodder galega, red clover, and alfalfa were subjected to lactic acid fermentation in 27 variants of the experiment. Local strains (Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, and Lactobacillus sp. RS 4) and the collection strain Lactobacillus plantarum BS 933 appeared the most efficient (with reference to the rate and degree of acidogenesis, ratio of lactic and acetic acids, and dynamics of microflora) in fermenting fodder galega juice; Lactobacillus sp. RS 1, Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, Lactobacillus sp. RS 4, and L. plantarum BS 933 were the most efficient for red clover juice. Correction of alfalfa juice fermentation using the tested lactic acid bacterial strains appeared inefficient, which is explainable by its increased protein content and a low level of acids produced during fermentation.

The P-7 incompatibility group plasmids responsible for biodegradation of naphthalene and salicylate in fluorescent pseudomonads

Analysis of seven plasmids (77 to 135 kb in size) of the P-7 incompatibility group that are responsible for the biodegradation of naphthalene and salicylate has shown that the main natural host of IncP-7 plasmids is the species Pseudomonas fluorescens. The IncP-7 plasmids are structurally diverse and do not form groups, as is evident from their cluster analysis. The naphthalene catabolism genes of six of the IncP-7 plasmids are conservative and homologous to the catabolic genes of NAH7 and pDTG1 plasmids. The pAK5 plasmid contains the classical nahA gene, which codes for naphthalene dioxygenase, and the salicylate 5-hydroxylase gene (nagG) sequence, which makes the conversion of salicylate to gentisate possible.

Bacterial Degraders of Polycyclic Aromatic Hydrocarbons Isolated from Salt-Contaminated Soils and Bottom Sediments in Salt Mining Areas

Fifteen bacterial strains capable of utilizing naphthalene, phenanthrene, and biphenyl as the sole sources of carbon and energy were isolated from soils and bottom sediments contaminated with waste products generated by chemical- and salt-producing plants. Based on cultural, morphological, and chemotaxonomic characteristics, ten of these strains were identified as belonging to the genera Rhodococcus, Arthrobacter, Bacillus, and Pseudomonas. All ten strains were found to be halotolerant bacteria capable of growing in nutrient-rich media at NaCl concentrations of 1–1.5 M. With naphthalene as the sole source of carbon and energy, the strains could grow in a mineral medium with 1 M NaCl. Apart from being able to grow on naphthalene, six of the ten strains were able to grow on phenanthrene; three strains, on biphenyl; three strains, on octane; and one strain, on phenol. All of the strains were plasmid-bearing. The plasmids of the Pseudomonas sp. strains SN11, SN101, and G51 are conjugative, contain genes responsible for the degradation of naphthalene and salicylate, and are characterized by the same restriction fragment maps. The transconjugants that gained the plasmid from strain SN11 acquired the ability to grow at elevated NaCl concentrations. Microbial associations isolated from the same samples were able to grow at a NaCl concentration of 2.5 M.Fifteen bacterial strains capable of utilizing naphthalene, phenanthrene, and biphenyl as the sole sources of carbon and energy were isolated from soils and bottom sediments contaminated with waste products generated by chemical- and salt-producing plants. Based on cultural, morphological, and chemotaxonomic characteristics, ten of these strains were identified as belonging to the genera Rhodococcus, Arthrobacter, Bacillus, and Pseudomonas. All ten strains were found to be halotolerant bacteria capable of growing in nutrient-rich media at NaCl concentrations of 1–1.5 M. With naphthalene as the sole source of carbon and energy, the strains could grow in a mineral medium with 1 M NaCl. Apart from being able to grow on naphthalene, six of the ten strains were able to grow on phenanthrene; three strains, on biphenyl; three strains, on octane; and one strain, on phenol. All of the strains were plasmid-bearing. The plasmids of the Pseudomonas sp. strains SN11, SN101, and G51 are conjugative, contain genes responsible for the degradation of naphthalene and salicylate, and are characterized by the same restriction fragment maps. The transconjugants that gained the plasmid from strain SN11 acquired the ability to grow at elevated NaCl concentrations. Microbial associations isolated from the same samples were able to grow at a NaCl concentration of 2.5 M.

Ultramicrobacteria: Formation of the concept and contribution of ultramicrobacteria to biology

Ultramicrobacteria (UMB) are species of the domain Bacteria characterized by very small sizes of proliferating cells (less than 0.1 μm3 in volume) and small genomes (3.2 to 0.58 Mb). Some authors use the term nanobacteria as a synonym of UMB. Several tens of UMB species have been isolated from various natural habitats: sea water, soil, silt, Greenland ice sheet, permafrost soils, and intestines of humans and insects. Under laboratory conditions, they are cultivated on different nutrient media. In the second prokaryotic domain, the Archaea, ultrasmall forms (ultramicroarchaea) have also been described, including nanoarchaea (members of the genus Nanoarchaeum) with a cell volume of less than 0.1 μm3. The term nanobacteria is used in the literature also to denote ultrasmall bacterium-like particles occurring in rocks, sands, soils, deep sub-surface layers, meteorites, and clinical samples. The systematic position and the capacity for self-reproduction of these particles are still unclear. The cultured UMB forms are characterized by highly diverse morphology, ultrastructural organization, physiology, biochemistry, and ecology. UMB form three groups according to the type of cell wall structure and the reaction to Gram staining: (1) gram-negative, (2) gram-positive, and (3) cell wall-lacking. Their cells divide by constriction, septation, or budding. The unique processes performed by UMB are dehalorespiration and obligate or facultative epibiotic parasitism. The UMB that synthesize organic compounds in ocean waters with the involvement of proteorhodopsin play a great role in the biosphere. UMB have been found in seven large phylogenetic groups of prokaryotes, where their closest relatives are organisms with larger cells typical of bacteria, which is evidence of the polyphyletic origin of the currently known UMB species and the reductive mode of their evolution.