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Open Access Highly Accessed Research article

Isolation and characterization of diverse antimicrobial lipopeptides produced by Citrobacter and Enterobacter

Santi M Mandal1, Shalley Sharma2, Anil Kumar Pinnaka2, Annu Kumari2 and Suresh Korpole2*

Author affiliations

1 Central Research Facility, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India

2 MTCC and Gene Bank, CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India

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Citation and License

BMC Microbiology 2013, 13:152  doi:10.1186/1471-2180-13-152

Published: 8 July 2013

Abstract

Background

Increasing multidrug-resistance in bacteria resulted in a greater need to find alternative antimicrobial substances that can be used for clinical applications or preservation of food and dairy products. Research on antimicrobial peptides including lipopeptides exhibiting both narrow and broad spectrum inhibition activities is increasing in the recent past. Therefore, the present study was aimed at isolation and characterization of antimicrobial lipopeptide producing bacterial strains from fecal contaminated soil sample.

Results

The phenotypic and 16S rRNA gene sequence analysis of all isolates identified them as different species of Gram-negative genera Citrobacter and Enterobacter. They exhibited common phenotypic traits like citrate utilization, oxidase negative and facultative anaerobic growth. The HPLC analysis of solvent extracts obtained from cell free fermented broth revealed the presence of multiple antimicrobial lipopeptides. The comprehensive mass spectral analysis (MALDI-TOF MS and GC-MS) of HPLC purified fractions of different isolates revealed that the lipopeptides varied in their molecular weight between (m/z) 607.21 to 1536.16 Da. Isomers of mass ion m/z 984/985 Da was produced by all strains. The 1495 Da lipopeptides produced by strains S-3 and S-11 were fengycin analogues and most active against all strains. While amino acid analysis of lipopeptides suggested most of them had similar composition as in iturins, fengycins, kurstakins and surfactins, differences in their β-hydroxy fatty acid content proposed them to be isoforms of these lipopeptides.

Conclusion

Although antimicrobial producing strains can be used as biocontrol agents in food preservation, strains with ability to produce multiple antimicrobial lipopeptides have potential applications in biotechnology sectors such as pharmaceutical and cosmetic industry. This is the first report on antibacterial lipopeptides production by strains of Citrobacter and Enterobacter.

Keywords:
Citrobacter; Enterobacter; Antimicrobial lipopeptide; MALDI and phylogenetic analysis