Detection and characterization of denitrifying bacteria from a permanently ice-covered Antarctic Lake

Denitrifying bacterial strains were isolated from Lake Bonney,apermanently ice-covered and chemically stratified lake in theMcMurdo dry valley region of Antarctica, using complex mediaat4 °C. Three strains, identified as denitrifiers bytheirability to produce nitrous oxide using nitrate or nitrite as arespiratory substrate, were characterized as to theirtemperatureand salinity optima for aerobic growth in batch culture; allthreewere psychrophilic and moderately halophilic. Maximum growthratesof near 0.024 h^–1 were measured for all three strains.Growthrates projected to occur at in situ temperature andsalinityimply generation times on the order of 100 h. Species specificpolyclonal antisera were prepared against two of the strains,ELB17 (from the east lobe of the lake at 17 m) and WLB20 (fromthewest lobe at 20 m). Both strains were subsequently detectedandenumerated in the lake using the antisera. ELB17 was presentinboth lobes below the chemocline, while WLB20 was present inthewest lobe below the chemocline but only in surface waters oftheeast lobe. These distributions are related to the observedchemicaldistributions which imply the occurrence of denitrification inthewest lobe of the lake and not in the east lobe.     

Studies on the factors influencing larval settlement in Balanus amphitrite and Mytilus galloprovincialis

Understanding of factors influencing settlement(attachment and metamorphosis) of marine invertebratelarvae is of great importance in aquaculture andcontrol of biofouling. The influence of two factors onsettlement of larvae was assessed from two separateinvestigations: 1, the influence of age (endogenousfactor) on cyprids of the barnacle Balanusamphitrite; and 2, the influence of a microbial film(exogenous factor) on pediveligers of the mussel Mytilus galloprovincialis.The settlement response of cypris larvae of B.amphitrite was found to be age-dependent. Oldercyprids responded more readily to settlement factorsthan newly molted ones. In M.galloprovincialis, competent pediveligers settled inresponse to a microbial filmed surface but not toan unfilmed surface. Moreover, a factor with MW of lessthan 5000 dalton, derived from culture medium of abacterial strain C1.1 (Pseudomonas-Alteromonasgroup), induced the settlement of M. galloprovincialis larvae.Thus, marine invertebrate larvae may require a periodof competence acquisition, during which they arepoorly responsive to settlement inducers. Uponacquisition of competence, larvae readily respondto external cues (e.g. microbial film, bacterialextracellular products).     

Differential effects of sodium ions on motility in the homoacetogenic bacteriaAcetobacterium woodii andSporomusa sphaeroides

The strictly anaerobic homoacetogenic bacteria Acetobacterium woodii and Sporomusa sphaeroides differ with respect to their energy metabolism. Since growth as well as acetate and ATP formation of A. woodii is strictly dependent on Na⁺, but that of S. sphaeroides is not, the question arose whether these organisms also use different coupling ions for mechanical work, i.e. flagellar rotation. During growth on fructose in the presence of Na⁺ (50 mM), cells of A. woodii were vigorously motile, as judged by light microscopy. At low Na⁺ concentrations (0.3 mM), the growth rate decreased by only 15%, but the cells were completely non-motile. Addition of Na⁺ to such cultures restored motility instantaneously. Motility, as determined in swarm agar tubes, was strictly dependent on Na⁺; Li⁺, but not K⁺ partly substituted for Na⁺. Of the amilorides tested, phenamil proved to be a specific inhibitor of the flagellar motor of A. woodii. Growth and motility of S. sphaeroides was neither dependent on Na⁺ nor inhibited by amiloride derivatives. These results indicate that flagellar rotation is driven by Δμ_Na ⁺ in A. woodii, but by Δμ_H ⁺ in S. sphaeroides. Received: 30 May 1995 / Accepted: 31 August 1995     

Characterization of Superoxide dismutase genes from Gram-positive bacteria by polymerase chain reaction using degenerate primers

Abstract An internal fragment representing approximately 85% of sod genes from seven Gram-positive bacteria was amplified by using degenerate primers in a polymerase chain reaction assay. The DNA sequences of sod polymerase chain reaction products from Clostridium perfringens, Enterococcus faecalis, Enterococcus faecium, Lactococcus lactis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae , and Streptococcus pyogenes were determined. Comparisons of their deduced amino acid sequences with those of the corresponding regions of the SOD proteins from Bacillus stearothermophilus, Listeria monocytogenes , and Streptococcus mutans revealed strong relatedness. Phylogenetic analysis of SOD peptides showed that members of the genera Streptococcus and those of the genera Enterococcus constitute two well-supported monophyletic groups. The method described in this study provides a means for easy recovery of sod genes and the construction of sod mutants of various Gram-positive pathogens.     

Utilisation of Ulva rigida biomass in the Venice Lagoon (Italy): biotransformation in compost

In the Venice Lagoon (Italy), about 10⁶ t (wet weight) of Ulva rigida biomass are produced annually as one of the major results of eutrophication. Harvests have been initiated to reduce negative impacts of this biomass, however, due to the high costs of such effort, only 40 000 t yr^-1 are currently being collected. At the moment, biotransformation into compost seems to be the only feasible technology for utilising large quantities of Ulva biomass. We describe and discuss here a successful composting strategy together with the chemico-physical and microbiological characteristics of the resultant composts. Our composting experiments were conducted at a scale of 20 t. The composting technology utilises large proportions (70–90%) of Ulva biomass and results in a valuable, high-quality end product (compost and compost-based products). This process and the resulting products represents a relatively simple way of utilising the Ulva biomass produced annually in the Venice Lagoon.     

Resonance Raman resolution of a-, b- and c-type cytochromes in membrane vesicles of alkalophilic bateria

Resonance Raman spectroscopy has been used to obtain complete spectra of each individual cytochrome type — a, b and c — in the reduced state within membrane vesicle preparations from two species of obligately alkalophilic bacteria: Bacillus alcalophilus and Bacillus firmus RAB. The vibrational spectra, in the range 250–1700 cm^?1, were obtained with tunable dye laser excitation in the wavelength range 550–600 nm tuned to resonance with the appropriate reduced alpha band maximum for the cytochrome type of interest. The spectra reveal details which serve to characterize the specific type of cytochrome as well as to confirm the similarity of the heme prosthetic group to previously well-characterized cytochromes of the the a- b- or c-type. Preliminary evidence in support of heterogeneity of b-type, and possibly a-type cytochromes, or of heme-heme interaction within the membrane is presented.     

Nitrogen fixation efficiency,natural15N abundance,and morphology of mesquite (Prosopis glandulosa) root nodules

Summary The relative nitrogen fixation efficiencies (RE 1-[H₂ evolved÷C₂H₂ reduced]·100) of four mesquite (Prosopis glandulosa var.torreyana) rhizobia (Strains WR 1001, WR 1002, L5, L9) and a cowpea rhizobia (Strain 176A32) on mesquite were evaluated in a glasshouse experiment. Plant yield, shoot N accumulation, and the natural¹⁵N abundance (¹⁵N) of nodule tissue were determined. Strain WR 1002 failed to nodulate mesquite and strain L5 produced ineffective nodules. Among the three effective strains (WR 1001, L9, 176A32) the cowpea strain (176A32) and strain L9 had significantly higher RE than strain WR 1001. Differences in RE, however, were not accompanied by significantly higher plant yield and shoot N accumulation. The difference in¹⁵N abundance between foliar tissue and nodules (nodules minus leaves) was 0.47 ¹⁵N for the ineffective L5 nodules, while for the effective WR 1001, L9, and 176A32 nodules, respectively, this difference was 8.35, 7.81, and 8.35 ¹⁵N. This indicates a similar relationship between N₂-fixing effectiveness and natural¹⁵N enrichment of nodules that was previously observed in soybeans (Glycine max, L. Merr.). Strains WR 1001 and L9 produced elongate, indeterminate nodules typical for mesquite. The ineffective L5 nodules had few infected cells and an abundance of cortical amyloplasts. Mesquite nodules produced by the cowpea strain were spherical and were somewhat more similar in internal morphology to determinate nodules typical of cowpea than indeterminate nodules normally associated with mesquite.     

Time-resolved microfluorescence for measuring coenzyme F420 in Methanobacterium thermoautotrophicum

Abstract The time course of photobleaching and the nanosecond fluorescence decay have been measured from microscopic samples of methanogenic bacteria, to our knowledge the first application of these methods in this field. Decay times of about 1 ns and 3 ns were obtained for the specific coenzymes F₄₂₀ and 7-methylpterin, respectively. In contrast to methylpterin and other fluorescent compounds the intensity of F₄₂₀ fluorescence was reduced selectively due to photobleaching. This effect, as well as the different decay time constants could be used to discriminate F₄₂₀ from other fluorescent components. In addition, active and inactive bacterial cells could be differentiated following the course of photobleaching.     

Increase in proteinase activity in the cellular slime mould Polysphondylium pallidum induced by bacteria

Abstract Polysphondylium pallidum strain PPHU8 grown in association with bacteria contains aspartic and cysteine proteinases. When myxamoebae were grown in axenic medium the contribution of cysteine proteinases was much lower. The proteinase activity could be altered by addition of heat-killed bacteria to axenically growing cells. This was detected as an increase in the specific activity towards N -benzoyl-L-prolyl-L-phenylalanyl-L-arginine- p -nitroanilide, a cysteine proteinase substrate, and by the appearance of cysteine proteinase bands after electrophoretic analysis. The changes were inhibited by cycloheximide, azide and dinitrophenol. All the available evidence suggests that they are due to the de novo synthesis of cysteine proteinases.     

Purification and some properties of a soluble cytochrome (cytochrome c-551) from Erythrobacter species strain OCh 114

A soluble cytochrome, cytochrome c-551 was purified from an aerobic photosynthetic bacterium Erythrobacter species strain OCh 114 (ATCC No. 33942) by ammonium sulfate fractionation, ion-exchange chromatography and gel-filtration. The cytochrome had absorption maxima at 277, 410, and 524–525 nm in the oxidized form, and at 415, 522, and 550.5 nm in the reduced form. At 77 K, the -band of the absorption spectrum of the reduced form split in two at 547 and 549 nm. The millimolar absorption coefficient at 550.5 nm was 26.8 mM^-1 cm^-1 in the reduced form. This cytochrome was an acidic protein with an isoelectric point of 4.9. Its molecular weight was determined to be 15,000 by gel-filtration on Sephadex G-100 and 14,500 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The midpoint potential of this cytochrome was +250 mV at pH 7.0. This cytochrome did not bind CO.