Utilization of cathodic hydrogen by hydrogen-oxidizing bacteria

Summary Hydrogen is consumed by methanogenic, sulphate-reducing, and homoacetogenic bacteria and members of these bacterial groups are able to grow chemolithotrophically with hydrogen as sole energy source. Cathodic hydrogen consumption by sulphate-reducing bacteria has been proposed as one of the factors in the anaerobic corrosion of metals. Desulfovibrio spp. were able to utilize cathodic hydrogen from mild steel as the only source of energy for growth with sulphate or nitrate as terminal electron acceptor. Other hydrogen-oxidizing bacteria such as Methanospirillum hungatei, Acetobacterium woodii and Wolinella succinogenes were also able to utilize cathodic hydrogen from mild steel for energy generation and growth. Weight loss studies of mild steel coupons under different growth conditions of Desulfovibrio spp. indicated that hydrogen removal alone is not the cause of corrosion and the depolarization phenomenon probably plays a role only in the initiation of the anaerobic microbial corrosion process.     

Nitrogen assimilation in opaque and normal sorghum during grain development

Activity of key nitrogen assimilating enzymes was studied in developing grains of high-lysine opaque sorghum P-721 and normal sorghum CSV-5. The higher percentage of protein in opaque sorghum was mainly due to lower starch content since protein per grain was less than in CSV-5. During grain development, albufn and globulin decreased while prolafne and glutelin increased. Prolafne content in CSV-5 was higher than in opaque sorghum. Average nitrate reductase activity in flag and long leaf were similar in both the varieties. The nitrate reductase activity decreased during grain development. Glutamate dehydrogenase activity was higher during early development and lower at later stages in opaque sorghum than in CSV-5. Glutamate oxaloacetate transaminase activity was higher and glutamine synthetase lower in opaque sorghum than in CSV-5 grains during development. Glutamate synthase activity was higher in opaque sorghum up to day 20 and lower thereafter than in CSV-5. It is suggested that reduced activities of glutamine synthetase as well as glutamate synthase in opaque sorghum as compared to CSV-5 during later stages of development may restrict protein accumulation in the former.     

Assimilatory reduction of sulfate and sulfite by methanogenic bacteria.

A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and delta H grew well with S0, SO3(2-), or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with SO4(2-) as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on SO4(2-) or SO2(2-) and Methanobacterium thermoautotrophicum Marburg on SO3(2-) but not to growth of strain delta H on SO3(2-). Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on SO4(2-), SO3(2-), thiosulfate, and S0. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S0, SO3(2-), or thiosulfate as the sole sulfur source.     

Investigation of mercaptans,organic sulfides,and inorganic sulfur compounds as sulfur sources for the growth of methanogenic bacteria

A variety of compounds were investigated for use as sulfur sources for the growth of methanogenic bacteria.Methanococcus (Mc.) deltae, Mc. maripaludis, Methanobacterium (Mb.) speciesGC-2B, GC-3B, andMMY, Methanobrevibacter (Mbr.) ruminantium, andMethanosarcina (Ms.) barkeri strain 227 grew well with sulfide, S^o, thiosulfate, or cysteine as sole sulfur source.Mbr. ruminatium was able to grow on SO ₄ ⁼ or SO ₃ ⁼ , andMs. barkeri strain 227 was able to grow on SO ₃ ⁼ , but not on SO ₄ ⁼ as a sole sulfur source.Mc. jannaschii grew with sulfide, S^o, thiosulfate or SO ₃ ⁼ , but not on cysteine or SO ₄ ⁼ as sole surface source.Mc. thermolithotrophicus, Mc. jannaschii, Mc. deltae, andMb. thermoautotrophicum strains Marburg and H were able to grow with methanethiol, ethanethiol,n-propanethiol,n-butanethiol, methyl sulfide, dimethyl sulfoxide, ethyl sulfide, or CS₂ as a sulfur source, when very low levels (20–30 M) of sulfide were present; no growth occurred on 5–100 M sulfide alone. Methanethiol, ethanethiol, and methyl sulfide-using cultures produced sulfide during growth.     

Effects of temperature,salinity and agitation on byssus thread formation of zebra musselDreissena polymorpha

Byssus thread production ofD. polymorpha under different conditions of temperature, salinity and agitation were studied in the laboratory. The acclimation to salinity and temperature greatly affects the byssus production ofD. polymorpha. Byssus production of mussels was significantly reduced when temperature increased beyond 20°C and decreased below 10°C. Mussels with cut threads (for counting), produced a substantially increased number of threads. However, mussels with uncut byssus threads were comparatively more mobile. Byssus production of mussels did not vary significantly at salinities up to 3. Beyond this salinity byssus production was reduced significantly. Mussels increased their byssus production with increasing frequency of agitation.     

Phosphorylation on histidine is accompanied by localized structural changes in the phosphocarrier protein, HPr from Bacillus subtilis.

The histidine-containing protein (HPr) of bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) serves a central role in a series of phosphotransfer reactions used for the translocation of sugars across cell membranes. These studies report the high-definition solution structures of both the unphosphorylated and histidine phosphorylated (P-His) forms of HPr from Bacillus subtilis. Consistent with previous NMR studies, local conformational adjustments occur upon phosphorylation of His 15, which positions the phosphate group to serve as a hydrogen bond acceptor for the amide protons of Ala 16 and Arg 17 and to interact favorably with the alpha-helix macrodipole. However, the positively charged side chain of the highly conserved Arg 17 does not appear to interact directly with phospho-His 15, suggesting that Arg 17 plays a role in the recognition of other PTS enzymes or in phosphotransfer reactions directly. Unlike the results reported for Escherichia coli P-His HPr (Van Nuland NA, Boelens R, Scheek RM, Robillard GT, 1995, J Mol Biol 246:180-193), our data indicate that phosphorylation of His 15 is not accompanied by adoption of unfavorable backbone conformations for active site residues in B. subtilis P-Ser HPr.