Biosurfactant Production by Bacillus tequilensis ZSB10 : Structural Characterization, Physicochemical, and Antifungal Properties

Authentication of putative competitive bacterial endophytes of rice by re-isolation and DNA fingerprinting assay

AIM

The plant-growth-promoting putative competitive endophytes offer significant benefits to sustainable agriculture. The unworthy opportunistic and passenger endophytes are inevitable during the isolation of putative competitive endophytes. This study aimed to discriminate the putative competitive endophytes undoubtedly from the opportunistic and passenger endophytes.

METHODS AND RESULTS

The newly-isolated endophytes from field-grown rice were inoculated to 5-days old rice seedlings under gnotobiotic conditions. Re-isolation of the inoculated strains from the root surface, inner tissues of the whole plant, root, and shoot was performed after 5-days. All the re-isolated colonies were compared with native isolate for the homology by BOX-A1R-based repetitive extragenic palindromic-PCR (BOX-PCR) and enterobacterial repetitive intergenic consensus (ERIC-PCR) DNA fingerprints. The results revealed that the putative competitive endophyte (RE25 and RE10) showed positive for re-isolation and BOX and ERIC fingerprints for the whole plant, root, and shoot. The opportunistic (RE27 and RE8) and passenger endophytes (RE44 and RE18) failed in re-isolation either from root or shoot. The epiphytes (ZSB15 and Az204) showed negative for endophytic re-isolation and positive for surface colonization.

CONCLUSION

This modified procedure can discriminate the putative competitive endophytes from others.

SIGNIFICANCE AND IMPACT OF THE STUDY

Eliminating the opportunistic and passenger endophytes and epiphytes early by this method would help develop endophytic inoculants to enhance rice productivity.

Recent Antimicrobial Responses of Halophilic Microbes in Clinical Pathogens

Microbial pathogens that cause severe infections and are resistant to drugs are simultaneously becoming more active. This urgently calls for novel effective antibiotics. Organisms from extreme environments are known to synthesize novel bioprospecting molecules for biomedical applications due to their peculiar characteristics of growth and physiological conditions. Antimicrobial developments from hypersaline environments, such as lagoons, estuaries, and salterns, accommodate several halophilic microbes. Salinity is a distinctive environmental factor that continuously promotes the metabolic adaptation and flexibility of halophilic microbes for their survival at minimum nutritional requirements. A genetic adaptation to extreme solar radiation, ionic strength, and desiccation makes them promising candidates for drug discovery. More microbiota identified via sequencing and ‘omics’ approaches signify the hypersaline environments where compounds are produced. Microbial genera such as Bacillus, Actinobacteria, Halorubrum and Aspergillus are producing a substantial number of antimicrobial compounds. Several strategies were applied for producing novel antimicrobials from halophiles including a consortia approach. Promising results indicate that halophilic microbes can be utilised as prolific sources of bioactive metabolites with pharmaceutical potentialto expand natural product research towards diverse phylogenetic microbial groups which inhabit salterns. The present study reviews interesting antimicrobial compounds retrieved from microbial sources of various saltern environments, with a discussion of their potency in providing novel drugs against clinically drug-resistant microbes.