Among several animals,
Rattus rattus
(rat) lives in polluted environments
and feeds on organic waste/small
invertebrates, suggesting the presence of inherent mechanisms to thwart
infections. In this study, we isolated gut bacteria of rats for their
antibacterial activities. Using antibacterial assays, the findings
showed that the conditioned media from selected bacteria exhibited
bactericidal activities against Gram-negative (
Escherichia
coli
K1,
Klebsiella pneumoniae
,
Pseudomonas aeruginosa
,
Serratia marcescens
, and
Salmonella
enterica
) and Gram-positive (
Bacillus
cereus
, methicillin-resistant
Staphylococcus
aureus
, and
Streptococcus pyogenes
) pathogenic bacteria. The conditioned media retained their antibacterial
properties upon heat treatment at boiling temperature for 10 min.
Using MTT assays, the conditioned media showed minimal cytotoxic effects
against human keratinocyte cells. Active conditioned media were subjected
to tandem mass spectrometry, and the results showed that conditioned
media from
Bacillus subtilis
produced
a large repertoire of surfactin and iturin A (lipopeptides) molecules.
To our knowledge, this is the first report of isolation of lipopeptides
from bacteria isolated from the rat gut. In short, these findings
are important and provide a platform to develop effective antibacterial
drugs.