Background The use of chemical fungicides against fungal pathogens adversely affects soil and plant health thereby resulting in overall environmental hazards. Therefore, biological source for obtaining antifungal agents is considered as an environment-friendly alternative for controlling fungal pathogens. Results In this study, seven endophytic bacteria were isolated from sugarcane leaves and screened for its antifungal activity against 10 fungal isolates belonging to the genera Alternaria, Cochliobolus, Curvularia, Fusarium, Neodeightonia, Phomopsis and Saccharicola isolated from diseased leaves of sugarcane. Among the seven bacterial isolates, SCB-1 showed potent antagonistic activity against the tested fungi. Based on the phenotypic data, Fatty Acid Methyl Esters (FAME) and 16S rRNA gene sequence analysis, the isolate SCB-1 was identified as Bacillus subtilis . The bacterial isolate was screened negative for chitinase production; however, chloroform and methanol extracts of the bacterial culture caused significant inhibition in the growth of the fungal isolates on semisolid media. Volatile component assay showed highest inhibitory activity against Saccharicola bicolor (SC1.4). A PCR based study detected the presence of the genes involved in biosynthesis of surfactin, bacillaene, difficidin, macrolactins and fengycin. Mass spectrometric analysis of the bacterial extract detected the presence of antifungal lipopeptide surfactin, but other metabolites were not detected. The biocontrol activity of the bacterial isolate was established when bacterial pretreated mung bean seeds were able to resist Fusarium infection, however, the untreated seeds failed to germinate. Conclusion The antifungal potential of isolate Bacillus subtilis SCB-1 was established against taxonomically diverse fungal pathogens including the genera Saccharicola , Cochliobolus, Alternaria and Fusarium . The potent antifungal compound surfactin as well as volatiles produced by the bacterial isolate could be responsible for its bio-control activity against fungal infections. Electronic supplementary material The online version of this article (10.1186/s12866-019-1440-8) contains supplementary material, which is available to authorized users.

The present study describes a lateral-flow-based dipstick immunoassay format using a novel hapten-protein-gold conjugate for the rapid screening of atrazine in water samples. The immunoassay is based on the competitive inhibition, in which a newly developed hapten-protein-gold conjugate competes with the free antigen present in the sample, for the limited antibody binding sites available at test zone on dipstick membrane, housed in a plastic cartridge. The tracer used as the detection reagent was prepared by first conjugating hapten (a derivative of atrazine) molecules to a carrier protein (bovine serum albumin) via its surface lysine residues and then linking colloidal gold nanoparticles to the hapten-protein conjugate via cysteine residues of the carrier protein. The developed conjugate showed a high level of stability as it did not show any significant loss of activity even after 8 weeks of storage at ambient conditions. The color developed due to conjugate, based on competitive inhibition approach, is correlated with the concentration of atrazine sample. The sensitivity of the developed dipstick was enhanced by gold nanoparticles, as an amplification tag, presenting detection limit of atrazine in standard water samples down to 1.0 ppb level. The kit could serve as a rapid screening methodology for visual screening of atrazine contamination of water samples within 5 min of analysis time, and, when coupled with a portable colorimeter, as an inexpensive semi-quantitative assay. The method reported can be useful for screening a large number of pesticides samples in a very short time in the field.

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