AUTHOR=Rungsirivanich Patthanasak , Parlindungan Elvina , O’Connor Paula M. , Field Des , Mahony Jennifer , Thongwai Narumol , van Sinderen Douwe 

TITLE=Simultaneous Production of Multiple Antimicrobial Compounds by Bacillus velezensis ML122-2 Isolated From Assam Tea Leaf [Camellia sinensis var. assamica (J.W.Mast.) Kitam.]

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.789362

DOI=10.3389/fmicb.2021.789362

ISSN=1664-302X

ABSTRACT=<p><italic>Bacillus velezensis</italic> ML122-2 is an antimicrobial-producing strain isolated from the leaf of Assam tea or Miang [<italic>Camellia sinensis</italic> var. <italic>assamica</italic> (J.W.Mast.) Kitam.]. The cell-free supernatant (CFS) of strain ML122-2 exhibits a broad-spectrum antimicrobial activity against various Gram-positive and Gram-negative bacteria as well as the mold <italic>Penicillium expansum</italic>. The genome of <italic>B. velezensis</italic> ML122-2 was sequenced and <italic>in silico</italic> analysis identified three potential bacteriocin-associated gene clusters, that is, those involved in the production of mersacidin, amylocyclicin, and LCI. Furthermore, six gene clusters exhibiting homology (75–100% DNA sequence identity) to those associated with the secondary metabolites bacilysin, bacillibactin, surfactin, macrolactin H, bacillaene, and plipastatin were identified. Individual antimicrobial activities produced by <italic>B. velezensis</italic> ML122-2 were purified and characterized by Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry analysis, revealing three antimicrobial peptides with molecular masses corresponding to surfactin, plipastatin, and amylocyclicin. Transcriptional analysis of specific genes associated with mersacidin (<italic>mrsA</italic>), amylocyclicin (<italic>acnA</italic>), plipastatin (<italic>ppsA</italic>), and surfactin (<italic>srfAA</italic>) production by <italic>B. velezensis</italic> ML122-2 showed that the first was not transcribed under the conditions tested, while the latter three were consistent with the presence of the associated peptides as determined by mass spectrometry analysis. These findings demonstrate that <italic>B. velezensis</italic> ML122-2 has the genetic capacity to produce a wide range of antimicrobial activities that may support a specific community structure and highlight the biotechnological properties of Assam tea.</p>