Effect of Fe on inorganic polyphosphate level in autotrophic and heterotrophic cells of Rhodospirillum rubrum.

Inorganic polyphosphate is involved in metal homeostasis in microorganisms. The aim of the study was to reveal differences in polyphosphate metabolism of Rhodospirillum rubrum under autotrophic and heterotrophic cultivation in the presence of Fe (2.3 mg Fe3+ L-1) and without Fe (traces). Heterotrophic conditions without Fe resulted in cell lysis and low biomass yield. High polyphosphate content and low exopolyphosphatase activity were observed in the cells cultivated autotrophically in the presence of Fe. The cells grown heterotrophically in the presence of Fe contained more phosphate and low-molecular polyphosphate; on the contrary, the content of the high molecular polyphosphate decreased in parallel with the increase in exopolyphosphatase activity. The possible involvement of Pi and polyphosphate to the formation of Fe-containing inclusions is discussed.

Individual stages of bacterial dichloromethane degradation mapped by carbon and chlorine stable isotope analysis.

The fractionation of carbon and chlorine stable isotopes of dichloromethane (CH2Cl2, DCM) upon dechlorination by cells of the aerobic methylotroph Methylobacterium extorquens DM4 and by purified DCM dehalogenases of the glutathione S-transferase family was analyzed. Isotope effects for individual steps of the multi-stage DCM degradation process, including transfer across the cell wall from the aqueous medium to the cell cytoplasm, dehalogenase binding, and catalytic reaction, were considered. The observed carbon and chlorine isotope fractionation accompanying DCM consumption by cell supensions and enzymes was mainly determined by the breaking of CCl bonds, and not by inflow of DCM into cells. Chlorine isotope effects of DCM dehalogenation were initially masked in high density cultures, presumably due to inverse isotope effects of non-specific DCM oxidation under conditions of oxygen excess. Glutathione cofactor supply remarkably affected the correlation of variations of DCM carbon and chlorine stable isotopes (Δδ13C/Δδ37Cl), increasing corresponding ratio from 7.2-8.6 to 9.6-10.5 under conditions of glutathione deficiency. This suggests that enzymatic reaction of DCM with glutathione thiolate may involve stepwise breaking and making of bonds with the carbon atom of DCM, unlike the uncatalyzed reaction, which is a one-stage process, as shown by quantum-chemical modeling.

Utilization of distillery wastewater for hydrogen production in one-stage and two-stage processes involving photofermentation.

In this study, distillery wastewater was treated by dark fermentation or photofermentation alone, and by sequential dark and photofermentation processes using anaerobic saccharolytic consortium and purple nonsulfur bacteria. Combination of dark and photofermentation resulted in the maximal H2 yield of 17.6L/L of distillery waste with chemical oxygen demand 40g/L. It is equivalent to 205kJ/L distillery wastewater and corresponds to recovery of approximately 4-8% of energy consumed during ethanol production. Optimal performance of photofermentation was observed at 20% concentration of pre-fermented distillery waste. In photofermentation, the range of the suitable distillery waste concentrations was extended and the H2 yield was improved by choosing the tolerant strain of purple bacteria Rhodobacter sphaeroides B-3059. After two stages, organic acids and sugars were completely consumed that means wastewater treatment concomitant to H2 production.

Long-term H2 photoproduction from starch by co-culture of Clostridium butyricum and Rhodobacter sphaeroides in a repeated batch process.

OBJECTIVES: To prove the possibility of efficient starch photofermentation in co-culture of heterotrophic and phototrophic bacteria over prolonged period. RESULTS: Repeated batch photofermentation of starch was demonstrated in co-culture Clostridium butyricum and Rhodobacter sphaeroides under microaerobic conditions. It continued 15 months without addition of new inoculum or pH regulation when using 4-5 g starch l-1 and 0.04 g yeast extract l-1. The complete degradation of starch without volatile fatty acids accumulation was shown in this co-culture. The average H2 yield of 5.2 mol/mol glucose was much higher than that in Clostridium monoculture. The species composition of co-culture was studied by q-PCR assay. The concentration of Clostridium cells in prolonged co-culture was lower than in monoculture and even in a single batch co-culture. This means that Clostridia growth was significantly limited whereas starch hydrolysis still took place. CONCLUSION: The prolonged repeated batch photofermentation of starch by co-culture C. butyricum and R. sphaeroides provided efficient H2 production without accumulation of organic acids under conditions of Clostridia limitation.

Inhibited growth of Clostridium butyricum in efficient H2-producing co-culture with Rhodobacter sphaeroides.

Cell number of Clostridium butyricum and Rhodobacter sphaeroides in co-culture was measured using q-PCR approach. During efficient H2 photoproduction from starch (6.2 mol H2/mol glucose), Clostridia growth and starch-hydrolyzing activity was partly suppressed. Apparently, the effect of R. sphaeroides towards C. butyricum was not attributed to altered Eh or pH values in the presence of purple bacteria. Further, disk-diffusion test proved that R. sphaeroides was capable of producing inhibitors against another purple bacterium, Rhodospirillum rubrum, but not against C. butyricum. We suggested that at initial cell number ratio C. butyricum:R. sphaeroides 1:1 purple bacteria outcompeted C. butyricum for yeast extract at its low concentration (80 mg/L). Under these conditions, the H2 yield was rather high (5.7 mol/mol). When the yeast extract concentration increased to 320 mg/L, this process was replaced by the low-yield H2 production (1.8 mol/mol) characteristic of Clostridia. However, increased percentage of purple bacteria in inoculum under these conditions prevented this shift. The outcome of competition depended on both the yeast extract concentration and cell number ratio. Apparently, the competition for yeast extract helped to maintain balance between fast-growing C. butyricum and slower-growing R. sphaeroides for efficient H2 photoproduction.

Suppositional area for the search of bacterial products for anticancer therapy.

It is well-known that bacteria can produce compounds which show anticancer effects. In present time, it is impossible to check all bacterial species on their possible production of anticancer compounds (AC) under different conditions. Thus, it is necessary to limit the area for search of bacterial products for the anticancer therapy. We propose that production of AC by bacteria is a part of microbial biological strategy under natural conditions. We propose that bacteria in soils, in water and on plants do not meet human tumors and their AC serve for the competition with eukaryotic organisms. Most probably, an epiphytic growth of bacilli is accompanied with production of compounds inhibiting eukaryotes. According to awaited profit for the AC-producing bacteria, the epiphytic groups of bacilli show inhibition of mycelial fungi which are a natural model of eukaryotic cells. An example of strain isolation and a primary test is presented.

Estimation of microbial methane generation and oxidation rates in the municipal solid waste landfill of Kaluga city, Russia.

Using a theoretical model and mass isotopic balance, biogas (methane and CO(2)) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34 x 10(6) tons of waste buried using a 'sandwich technique' (successive application of sand-clay and waste layers). The delta(13)C values of biogenic methane with respect to CO(2) were-56.8 (+/-2.5) per thousand, whereas the delta(13)C of CO(2) peaked at+9.12 per thousand (+1.4+/-2.3 per thousand on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO(2) reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by delta(13)C in the range of-50.6 to-38.2 per thousand, evidencing enrichment in (13)C, while the released carbon dioxide had delta(13)C of-23.3 to-4.04 per thousand, respectively. On the mass isotopic balance for the delta(13)C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(+/-1.4)x10(9) g C CH(4) yr(-1) or 5.3(+/-2.6)x10(6) m(3) CH(4) yr(-1). The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (+/-26) g C CH(4) m(-2) d(-1) (or 4 (+/-2) mol CH(4) m(-2) d(-1)) and 33 (+/-12) g C CH(4) m(-2) d(-1) (or 2.7 (+/-1) mol CH(4) m(-2) d(-1)), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(+/-7) g C CH(4) m(-2) d(-1) (or 1.1(+/-0.6) mol CH(4) m(-2) d(-1)) on average.