Characterization and genomic insight of surfactin-producing Bacillus velezensis and its biocontrol potential against pathogenic contamination in lettuce hydroponics.

Due to food borne pathogen, maintaining the viability of fresh fruits and vegetable is a great concern. Several strategies including microbial and plant-based formulations to reduce their infection and maintain quality of the fresh food are in practice. Currently, Bacillus has gained significant traction as a biocontrol agent for regulating diseases affecting a variety of agricultural and horticultural crops. Food-grade citric acid and plant growth-promoting rhizobacteria (PGPR) were used as antimicrobial agent, MIC results showed that PGPR (14.87 mm) and CA (20.25 mm) exhibited notable antimicrobial activity against E. coli. Lettuce treated with PGPR showed reduction in E. coli contamination, E. coli was detected at 3.30, 3.68 in control, and 2.7 log CFU/g in random root injury lettuce inoculated with PGPR KACC 21110 respectively. Random root injury showed a trend toward increasing E. coli internalization. The strains exhibited resistance to multiple antibiotics, including Imipenem, tetracycline, ampicillin, cefotaxime, cefoxitin, and ceftriaxone. Comprehensive data analysis revealed the presence of ten putative bacteriocin or bacteriocin-like gene clusters. The structure of lipopeptide homologs was characterized by using QTOF-MS/MS. The mass ion peaks attributed to surfactin homologs, surfactin A ion at m/z 1008.66, surfactin B, C at m/z 1022.67 and 1036.69. In addition to surfactin, a polyketide oxydifficidin and lipopeptide NO were extracted and detected from the extract of B. velezensis. Both isolates are key biocontrol agents and have significant potential in combating foodborne pathogens and can be utilized to explore novel antibacterial products for preventing pathogens in fresh produce.

Short Communication: Enterotoxin Genes and Antibiotic Susceptibility of Bacillus cereus Isolated from Garlic Chives and Agricultural Environment.

This study aims to investigate the enterotoxin profiles and antibiotic susceptibility of Bacillus cereus isolated from garlic chives and environmental samples. A total of 103 B. cereus isolates were used to identify enterotoxin genes, including hblA, hblC, hblD, nheA, nheB, and nheC. The hemolysin BL enterotoxin complex (hblACD) was detected in 38 isolates (36.9%), and the non-hemolytic enterotoxin complex (nheABC) was detected in 8 (7.8%) isolates. Forty-five isolates (43.7%) had hblACD and nheABC genes. B. cereus was resistant to ß-lactam antibiotics and susceptible to non-ß-lactam antibiotics. However, some B. cereus strains showed intermediate resistance to ß-lactam and non-ß-lactam antibiotics. B. cereus isolated from garlic chives showed intermediate resistance to cefotaxime (7.7%), rifampin (15.4%), clindamycin (30.8%), erythromycin (7.7%), and tetracycline (7.7%). B. cereus isolates from the agricultural environment were moderately resistant to cefotaxime (18.9%), rifampin (15.6%), clindamycin (12.2%), erythromycin (4.4%), and tetracycline (5.6%). Moreover, B. cereus isolates from garlic chives and cultivation environments could change their antibiotic resistance profile from susceptible to intermediate-resistant to rifampin, clindamycin, erythromycin, and tetracycline and exhibit multidrug resistance. These results indicate that continuous monitoring of B. cereus contamination in the produce and agricultural environment might be needed to ensure the safety of consuming fresh vegetables.