Characterization and phylogenetic analysis of novel polyene type antimicrobial metabolite producing actinomycetes from marine sediments:Bay of Bengal India

Objective:To isolate and indentify the promising antimicrobial metabolite producing Streptomyces strains from marine sediment samples from Andraprudesh coast of India.Methods:Antagonistic aetinomycetes were isolated by starch casein agar medium and modified nutrient agar medium with 1%glucose used as a base for primary screening.Significant antimicrobial metabolite producing strains were selected and identified by using biochemical and 16S rDNA level.Minimum inhibitory concentrations of the organic extracts were done by using broth micro dilution method.Results:Among the 210 actinomyeetes,64.3%exhibited activity against Gram positive bacteria,48.5%showed activity towards Cram negative bacteria,38.8%exhibited both Cram positive and negative bacteria and 80.85%isolates revealed significant antifungal activity.However,five isolates AP-5,AP-18,AP-41 and AP-70 showed significant antimicrobial activity.The analysis of cell wall hydrolysates showed the presence of LL-diaminopimelic acid and glycine in all the isolates.Sequencing analysis indicated that the isolates shared 98.5%-99.8%sequence identity to the 16S rDNA gene sequences of the Streptomyces taxons.The antimicrobial substances were extracted using hexane and ethyl acetate from spent medium in which strains were cultivated at 30X for five days.The antimicrobial activity was assessed using broth micro dilution technique.Each of the culture extracts from these five strains showed a typical polyenelike property.The lowest minimum inhibitory concentrations of ethyl acetate extracts against Escherichia coli and Cumularia lunula were 67.5 and 125.0μg/mL,respectively.Conclusions:It can be concluded that hexane and ethyl acetate soluble extracellular products of novel isolates are effective against pathogenic bacteria and fungi.

Cytotoxic (A549) and antimicrobial effects of Methylobacterium sp.isolate (ERI-135) from Nilgiris forest soil,India

Objective:To assess the antimicrobial and cytotoxic effects of Methylobacterium sp.isolated from soil sample of Doddabetta forest,Nilgiris,Western Ghats of Tamil Nadu.Methods:Isolation of Methylobacterium was performed from soils by serial dilution plate technique.The strain was grown in modified nutrient gulucose agar(MNGA)medium to study the morphology and biochemical characteristics.Methylobacterium sp.was screened for its antimicrobial activity against pathogenic bacteria and fungi.The strain was subjected to 16S rRNA analysis and was identified as Methylohacterium sp.The nucleotide sequence of the 16S rRNA gene of the isolate exhibited close similarity with other Methylobacterium sp.and has been submitted to Genbank.The antibacterial substances were extracted using chloroform and ethyl acetate from MNGA medium in which ERI-135 had grown for 5 d at 30℃.Cytotoxic effect was also studied.GC-MS analysis was carried out.The antimicrobial activity was assessed using broth micro dilution technique.Results:Ethyl acetate extract showed activity against bacteria such as Bacillus subtilis,Klebsiella pneumoniae(K.pneumoniae),Pseudomonas aeruginosa,Salmonella typkimurium,Shigella flexneri,Enterobacter aerogenes,Staphylococcus aureu and Staphylococcus epidermidis(S.epidermidis)and fungi such as,Candida albicans and Trichophyton rubrum.The lowest minimum inhibitory concentrations were:250μg/mL against 5.epidermidis and 250μg/mL against K.pneumonia.The isolate had the ability to produce enzymes such as protease.The exyract showed cytotoxic effect in human adenocarcinoma cancer cell line(A549).GC-MS analysis showed the presence of isovaleric acid(3.64%),2-Methylbulanoic acid(5.03%),isobutyramide(5.05%),N,Noimethylformamide-di-t-butylacetal(9.79%),benzeneacetamide(15.56%),octyl butyl phthalate(3.59%)and diisooctyl phthalate(5.79)in the extract.Conclusions:Methylobaeterium sp.(ERI-135)showed promising antibacterial and cytotoxic activity.This is the first report in the antimicrobial and cytotoxic effect of Methylobaeterium sp.

全颗粒饲料对奶牛生产性能的影响

饲料中的中性洗涤纤维(NDF)含量和饲料颗粒直径是影响瘤胃功能的重要因素。试验评估了以颗粒饲料为主的奶牛瘤胃健康情况、NDF消化率和生产性能。选取8头荷斯坦母牛(336±30 d,体重346±35 kg),随机分配到交叉重复试验组中,奶牛安置于牛栏,自由采食。试验期为3周,前两周是适应期,最后一周为数据收集期。各组饲粮原料相同,但物理形式不同,分为全混合日粮(TMR)和颗粒料(直径=8 mm)。两组间物理有效NDF(pe NDF)不同,TMR组为39.8%,颗粒料组为11.8%。在试验过程中,干物质采食量(DMI)、饮水量、瘤胃反刍时间、瘤胃温度和pH情况均记录。3周后收集粪样,确定潜在的可消化NDF总消化率(pdNDF)。每阶段结束后计算平均日增重和饲料转化率。颗粒料组的DMI、DMI/体重和饮水量更高。而两组间平均日增重和饲料转化率无显著差异。颗粒料组的瘤胃反刍时间为241 min·d-1低于TMR组的507 min·d-1。饲料的不同物理外形对瘤胃温度、瘤胃pH无显著影响。TMR组的pdNDF总消化率为90.25%高于颗粒料组的86.82%。试验结果表明,动物易接受完整的颗粒饲料,DMI较高,且反刍时间减少,但瘤胃pH无显著变化。TMR组的pdNDF消化率显著增加。尽管两组奶牛在DMI和纤维消化方面表现不同,但总体表现相似,两组饲料的保存时间与其物理形式有关。在短期内,提供能满足NDF需求的完全颗粒饲料可改善瘤胃健康状况和动物生产性能,而较长时间的数据则需要进一步试验。