Four facultatively alkalophilic isolates were purified from enrichment cultures initiated with lime-treated garden soil. Four isolates, OF1, OF3, OF4, and OF6, were obligately aerobic, spore-forming, gram-positive, motile rods which were capable of growth at both pH 7.5 and pH 10.5. Strains OF1 and OF6 grew best at the lower pH value; and whereas growth of these strains at pH 10.5 was completely dependent on added Na+, growth at pH 7.5 was only partially dependent on added Na+. Strains OF3 and OF4 grew better at pH 10.5 than at pH 7.5, with strain OF3 growing modestly over its entire pH range, while OF4 grew well. Growth of OF3 and OF4 was completely dependent on added Na+ at both pH 7.5 and pH 10.5. DNA-DNA hybridization studies indicated that OF1 and OF6 are closely related strains but are not related to the other isolates, BaciUus subtilis, or two previously studied obligately alkalophilic bacilli. OF3 was unrelated to any of the other organisms examined in the study, whereas OF4 showed complete homology with obligately alkalophilic BacUlus firmus RAB. All four isolates maintained a cytoplasmic pH that was considerably lower than the external pH when the latter was 10.5. Although substantial transmembrane electrical potentials were observed, the total electrochemical proton gradient (AAWH+) was low at pH 10.5 in all the strains. By contrast, A4iH+ was substantial at pH 7.5 and at that pH was composed entirely of an electrical potential. These results are in contrast to previous findings that obligately alkalophilic bacilli generate only small electrical potentials at near neutral pH. All the isolates exhibited substantial rates of respiration as measured by oxygen consumption. Neither respiration nor NADH oxidation by everted membrane vesicles was significantly stimulated by Na+. Analyses of reduced versus oxidized difference spectra of membranes from OF4 showed that the total membrane cytochrome content was considerably higher in cells grown at pH 10.5 than at pH 7.5, with the levels of c-and a-type cytochromes exhibiting the largest pH-dependent differences. Initial examination of membrane protein profiles on gel electrophoresis also indicated a number of changes in pattern in each isolate, depending on the growth pH.Alkalophilic bacteria, which grow well in a pH range from 10 to 11, are of ecological, industrial, and basic bioenergetic interest (8, 13). Studies of alkalophiles conducted thus far in our laboratory have focused on bacilli that are obligately alkalophilic. These species, especially Bacillus alcalophilus and Bacillusfirmus RAB, cannot grow in the neutral range of pH and grow well only at pH 9.0 and above (4, 5). Other investigators have studied different species of alkalophiles, mostly bacilli, that can grow both in the neutral and highly alkaline pH ranges (3, 10, 21). It is not yet clear what precludes growth of the obligate alkalophiles at neutral pH, although possible factors include compromise of membrane integrity at neutral pH (12) and poor function of the respiratory chain at neutral b...

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Manganese sulfide nanospheres (MnS‐NSs) prepared in situ via sonochemical process were characterized to investigate the effect of nanoscale MnS on antifungal potential against mycopathogens of rice viz. Fusarium verticillioides, Drechslera oryzae and Curvularia lunata. MnS‐NSs dispersed in aqueous medium resulted in significant inhibition of growth of all the test fungi (ED50 ≤ 18 μg/ml) at concentration much lower than standard commercial fungicides (captan and carbendazim with ED50 ≥ 230 μg/ml) against respective fungi. The maximum per cent inhibition (98 ± 1.4) was recorded against C. lunata with a minimum ED50 value of 14 μg/ml, followed by D. oryzae and F. verticillioides with ED50 values of 17 and 18 μg/ml, respectively. Nanopriming of rice seeds with MnS‐NSs at 35 μg/ml for 8 hr resulted in significant reduction in seed rot (76%) and seedling blight (89.13%) along with enhancement in percent germination, root length, shoot length, dry weight and vigour index of seedlings by 33.7%, 55%, 66.3%, 85.3% and 89.3%, respectively, compared with control. Hydropriming of seeds was found to control the seed health parameters less effectively than nanopriming.

Surface capped copper sulfide nano-aquaformulations were prepared by in situ combination of copper ions with sulfide ions using sonochemical method, followed by microwave irradiations, in the presence of capping agents. Prepared nano-aquaformulations were characterized for particle size, morphology and optical properties. The in vitro antifungal evaluations studies indicated multifold efficacy against Alternaria alternata, Drechslera oryzae and Curvularia lunata in comparison to standard used. The in vivo seed treatment on discoloured paddy seeds showed the optimum results on application @ 7lg/ml for 2 h in case of citrate capped copper sulfide nanoformulation (NCuS 3 ). Significant reduction in seed rot and seedling blight was observed with favourable effect on germination and growth parameters at this concentration.

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