Purification of membrane-bound polyvinyl alcohol oxidase in Pseudomonas sp. VM15C

Abstract Polyvinyl alcohol (PVA) was utilized by a symbiotic mixed culture which was composed of Pseudomonas putida VM15A and Pseudomonas sp. VM14C. The PVA oxidase was found in the culture fluid, membrane, and cytosol fractions of VM15C. The membrane-bound PVA oxidase was purified by several steps of chromatography. The enzyme (p I = 9.6) exhibited the maximum activity at pH 8.0 to 8.4 and 45°C, and utilized secondary alcohol as well as PVA. The enzyme showed the PVA dehydrogenating activity linking with phenazine ethosulfate, indicating the possibility that PVA oxidation is coupled with an electron transport chain on the bacterial membrane.     

Molecular Analysis of Plant Defense Responses to Plant Pathogens

A number of inducible plant responses are believed to contribute to disease resistance. These responses include the hypersensitive reaction, phytoalexin synthesis, and the production of chitinase, glucanase, and hydroxyproline-rich glycoproteins. Because of the coordinate induction of these responses, it has been difficult to determine whether they are functional defense responses, and if they are, how they specifically contribute to disease resistance. Recent developments in molecular biology have provided experimental techniques that will reveal the specific contribution of each response to disease resistance. In this paper, we describe a strategy to determine if the hypersensitive reaction is a functional plant defense mechanism.     

Characterization of initial events in bacterial surface colonization by two Pseudomonas species using image analysis

The processes leading to bacterial colonization on solidwater interfaces are adsorption, desorption, growth, and erosion. These processes have been measured individually in situ in a flowing system in real time using image analysis. Four different substrata (copper, silicon, 316 stainless-steel and glass) and 2 different bacterial species (Pseudomonas aeruginosa and Pseudomonas fluorescens) were used in the experiments. The flow was laminar (Re = 1.4) and the shear stress was kept constant during all experiments at 0.75 N m(-2). The surface roughness varied among the substrata from 0.002 mum (for silicon) to 0.015 mum (for copper). Surface free energies varied from 25.1 dynes cm(-1) for silicon to 31.2 dynes cm(-1) for copper. Cell curface hydrophobicity, reported as hydrocarbon partitioning values, ranged from 0.67 for Ps. fluorescens to 0.97 for Ps. aeruginosa.The adsorption rate coefficient varried by as much as a factor of 10 among the combinations of bacterial strain and substratum material, and was positively correlated with surface free energy, the surface roughness of the substratum, and the hydrophobicity of the cells. The probability of desorption decreased with increasing surface free energy and surface roughness of the substratum. Cell growth was inhibited on copper, but replication of cells overlying an initial cell layer was observed with increased exposure time to the cell-containing bulk water. A mathematical model describing cell accumulation on a substratum is presented.     

Isolation and characterization of fluorescent Pseudomonas associated with the roots of rice and banana grown in Sri Lanka

Bacterial populations in different parts of the rhizosphere of rice and banana in Sri lanka were examined. On rice, the number of aerobic bacteria and the population of fluorescent bacteria were higher in the rhizoplane as compared to the exorhizosphere. However, the opposite was observed with banana. Percentage of fluorescent bacteria was significantly higher on banana (10.8%) than on rice from the wet and dry zones of Sri Lanka (4.3% and 2.7%, respectively). In the endorhizosphere fraction of rice, bacterial populations were very low. Fluorescent bacteria were absent.Based on 33 phenotypical tests, 89 fluorescent isolates were grouped into 5 clusters. The three major clusters covered the isolates belonging to the Pseudomonas fluorescens-putida group, whereas the remaining small clusters contained other UV-fluorescent bacteria. SDS-PAGE of total cell proteins enabled classification of the isolates into one of 12 different protein-polymorphic types. Only a partial correlation was found between the latter classification and the phenotypical one. Cyanogenesis was observed with strains of P. fluorescens only. Isolates P. fluorescens RW9S1 and P. cepacia RW5P1 displayed a potent antagonism against several fungi.     

Regulation of amidase formation in mutants from Pseudomonas aeruginosa PAO lacking glutamine synthetase activity

The formation of amidase was studied in mutants from Pseudomonas aeruginosa PAO lacking glutamine synthetase activity. It appeared that catabolite repression of amidase synthesis by succinate was partially relieved when cellular growth was limited by glutamine. Under these conditions, a correlation between amidase and urease formation was observed. The results suggest that amidase formation in strain PAO is subject to nitrogen control and that glutamine or some compound derived from it mediates the nitrogen repression of amidase.     

Cytochrome b type oxidases in the respiratory chains of the phytopathogenic fluorescent bacteria Pseudomonas cichorii and Pseudomonas aptata

Membrane fragments from the phytopathogenic bacteria Pseudomonas cichorii and Pseudomonas aptata have been examined. A branched respiratory chain is operative in P. cichorii whereas a linear electron transport system characterizes the related bacterium P. aptata. Both species contain several b type cytochromes resolved by redox titration analysis, but no a type components may be detected. In contrast, only P. cichorii is endowed with c type cytochromes and hence with cytochrome c oxidase activity. Among the b type cytochromes, two high-potential components, with Em_7.0 at +250 mV and +380 mV, have been kinetically characterized and tentatively associated with cyanideresistant and cytochrome c oxidase activities, respectively. Cytochrome b-250 should correspond to the spectrally detectable cytochrome o whereas cytochrome b-380 is functionally similar to cytochrome b-410 described in Rhodopseudomonas capsulata. This conclusion seems to blur previous reported data on other obligate aerobes in which cytochrome o has been generally associated with cytochrome c oxidase and also suggests that a more accurate reconsideration of the actual physiological role of cyt. o in bacterial respiration is necessary. Furthermore the question arises whether cyt. b-410 like oxidases, i. e. high-potential b's similar to cyt. b-410 of R. capsulata, may be widely distributed among aerobes rather than restricted to facultative photosynthetic prokaryotes.     

Antibiotic-resistantArthrobacter sp. andPseudomonas sp. responses in the rhizosphere of blue grama after herbage removal

Summary Streptomycin-resistant Pseudomonas and Arthrobacter were isolated from semi-arid grassland soil and their relative responses in the rhizosphere of blue grama (Bouteloua gracilis) subjected to herbage removal were evaluated. Using plants grown in normal soil, the two bacteria showed differential responses to herbage removal, which were most marked in the rhizoplane, where the Pseudomonas showed a two-log unit increase over a 60 hour period, while Arthrobacter, in contrast, exhibited a one-log unit decrease in viable counts for at least 48 hours after defoliation, responses which are similar to those observed in root exudate medium experiments by earlier workers. These results suggest that the rhizoplane may be a critical environment for interaction of these two types of microorganisms, and that sequential responses of the root-associated soil microorganisms may occur after herbage removal from this important rangeland plant. These responses are most likely associated with increased exudate release following herbage removal, which has been best documented using blue grama grown under sterile conditions.     

Biocontrol: Bacillus penetrans and Related Parasites of Nematodes

Bacillus penetrans Mankau, 1975, previously described as Duboscqia penetrans Thorne 1940, is a candidate agent for biocontrol of nematodes. This review considers the life stages of this bacterium: vegetative growth phase, colony fragmentation, sporogenesis, soil phase, spore attachment, and penetration into larvae of root-knot nematodes. The morphology of the microthallus colonies and the unusual external features of the spore are discussed. Taxonomic affinities with the actinomycetes, particularly with the genus Pasteuria, are considered. Also discussed are other soil bacterial species that are potential biocontrol agents. Products of their bacterial fermentation in soil are toxic to nematodes, making them effective biocontrol agents.