Isolation of Bacillus spp. Bacteria from Soil for Production of Cellulase

Cellualse is one of the most important enzymes used in textile, detergent, paper, food and feed industries. Therefore, a study was undertaken to isolate Bacillus bacteria having the potential to produce cellulase from soil samples. 24 soil samples were analyzed and 54 presumptive Bacillus isolates were isolated after heating the soil samples at 80°C for 10 min. Among them 45 isolates showed enzyme activity ranging from 0.003 to 0.17 U/ml in test tubes containing 5 ml medium composed of (g/L) glucose 0.5 gm, peptone 0.75 gm, FeSO4 0.01 gm, KH2PO4 0.5 gm, and MgSO4 0.5 gm at 120 rpm, 37° C and pH 7. Among them 1RW, 2WS, 3YR, 4WT, 6 RR, and 9SS showed 0.17, 0.15, 0.14, 0.15, 0.147 and 0.14U/ml enzyme activities, respectively. Production of cellulase by these isolates was further scaled up to shake culture containing 50 ml medium similar to that used in test tube culture. Among the isolates 1 RW showed the maximum activity. This 1 RW was identified by API kit and showed that 59 % belongs to Bacillus licheniformis strain (51% confirmation) or Bacillus subtilis (31% confirmation). Further gene analysis is required to confirm the species. The genetic improvement study will make the isolate a good source of cellulase.

Effect of linoleic acid on reproduction and yeast–mycelium dimorphism in the Dutch elm disease pathogens

Elm populations from North America and Europe were devastated by Dutch elm disease (DED), which is a vascular disease caused by fungi from the genus Ophiostoma (Ascomycota). These pathogens feature a yeast–mycelium dimorphism that may be related to virulence by facilitating colonization of the host xylem. Cyclooxygenases (COX) have been proposed to modulate yeast–mycelium dimorphism of DED fungi, and homologs of cox genes have been found in the nuclear genome of O. novo-ulmi subsp. novo-ulmi. Linoleic acid, a substrate for COX, was reported to stimulate the formation of asexual and sexual reproduction structures in DED strains grown on complex media. We hypothesized that linoleic acid also induced mycelium production in liquid shake culture conditions. Linoleic acid was found to enhance the production of reproductive structures in sexual crosses conducted on a complex medium (elm sapwood agar), but was not sufficient for these structures to form on a minimal medium. In liquid shake cultures grown in a minimal medium, the addition of linoleic acid stimulated mycelial formation. Our results suggest that linoleic acid plays a role in reproduction and dimorphism in the DED pathogens.

Anti-CandidaProperties of Urauchimycins from Actinobacteria Associated withTrachymyrmexAnts

After decades of intensive searching for antimicrobial compounds derived from actinobacteria, the frequency of isolation of new molecules has decreased. To cope with this concern, studies have focused on the exploitation of actinobacteria from unexplored environments and actinobacteria symbionts of plants and animals. In this study, twenty-four actinobacteria strains isolated from workers ofTrachymyrmexants were evaluated for antifungal activity towards a variety ofCandidaspecies. Results revealed that seven strains inhibited the testedCandidaspecies.Streptomycessp. TD025 presented potent and broad spectrum of inhibition ofCandidaand was selected for the isolation of bioactive molecules. From liquid shake culture of this bacterium, we isolated the rare antimycin urauchimycins A and B. For the first time, these molecules were evaluated for antifungal activity against medically importantCandidaspecies. Both antimycins showed antifungal activity, especially urauchimycin B. This compound inhibited the growth of allCandidaspecies tested, with minimum inhibitory concentration values equivalent to the antifungal nystatin. Our results concur with the predictions that the attine ant-microbe symbiosis may be a source of bioactive metabolites for biotechnology and medical applications.

Effect of Carbendazim Resistance on Trichothecene Production and Aggressiveness of Fusarium graminearum

Fusarium graminearum (teleomorph, Gibberella zeae) causes head blight of cereals and contaminates grains with trichothecene mycotoxins that are harmful to humans and domesticated animals. Control of Fusarium head blight relies on carbendazim (MBC) in China, but resistance to MBC in F. graminearum is now widespread. Sixty-seven strains were evaluated for trichothecene production in shake culture or in the field. The strains included 60 wild-type strains (30 MBC-resistant and 30 MBC-sensitive), three MBC-resistant site-directed mutants at codon 167 in β2-tubulin, three MBC-sensitive site-directed mutants at codon 240 in β2-tubulin, and their MBC-sensitive wild-type progenitor strain ZF21. The incidence of infected spikelets and the amount of F. graminearum DNA in field grain (AFgDNA) also were evaluated for all strains. MBC resistance increased trichothecene production in shake culture or in the field. Although MBC resistance did not change the incidence of infected spikelets, it did increase AFgDNA. Tri5 gene expression increased in MBC-resistant strains grown in shake culture. We found a significant exponential relationship between trichothecene production and Tri5 gene expression in shake culture and a linear relationship between the incidence of infected spikelets or AFgDNA and trichothecene production in field grain.

Studies on the α-L-Arabinofuranosidase Complex from Sclerotinia fructigena in Relation to Brown Rot of Apple

α-L-Arabinofuranosidase (AF) was detected in apple fruitlets experimentally infected by Sclerotinia fructigena. In extracts of such fruitlets, three AF isoenzymes were separated by preparative isoelectric focusing. When the fungus was grown in shake culture with different carbon sources, AF was detected in each culture filtrate and mycelial homogenate. Although fungus growth and total AF varied with the carbon source, the AF isoenzyme pattern was similar in each instance to that obtained when grown on sodium polypectate. Each of the partially purified AF isoenzymes behaved differently in substrate specificity and inhibitor studies; however, each showed a specificity for α-L-arabino-furanosides. The two extracellular AF isoenzymes released monomeric arabinose when incubated with araban or apple cell walls. External AF III (pI 6·5) was more active on a substrate of apple cell wall material than external AF I (pI 3·0). The latter form of the enzyme was less susceptible to inhibition by either oxidized or unoxidized apple juice. Two isolates of Sclerotinia fructigena with low growth rate in vivo secreted no AF III in vitro.