Here we report the draft genomes and annotation of four N-acyl homoserine lactone (AHL)-producing members from the family Sphingomonadacae. Comparative genomic analyses of 62 Sphingomonadacae genomes were performed to gain insights into the distribution of the canonical luxI/R-type quorum sensing network within this family. Forty genomes contained at least one luxR homolog while the genome of Sphingobium yanoikuyae B1 contained seven Open Reading Frames (ORFs) that have significant homology to that of luxR. Thirty-three genomes contained at least one luxI homolog while the genomes of Sphingobium sp. SYK6, Sphingobium japonicum and Sphingobium lactosutens contained four luxI. Using phylogenetic analysis, the sphingomonad LuxR homologs formed five distinct clades with two minor clades located near the plant associated bacteria LuxR solo clade. This work for the first time shows that thirteen Sphingobium and one Sphingomonas genome(s) contain three convergently oriented genes composed of two tandem luxR genes proximal to one luxI (luxR-luxR-luxI) which we term convergent double luxR, luxI group. Interestingly, luxI solos were identified in two Sphingobium species and may represent species that contribute to AHL-based quorum sensing system by contributing AHL molecules but are unable to perceive AHLs as signals. This work provides the most comprehensive description of the luxI/R circuitry and genome-based taxonomical description of the available sphingomonad genomes to date indicating that the presence of luxR solos and luxI solos are not an uncommon feature in members of the Sphingomonadaceae family.

Foodborne diseases continue to pose a significant global health concern, causing a considerable number of deaths worldwide. In response to concerns surrounding bacterial resistance and the limitations of traditional antibiotics, there is a growing interest in exploring natural antibacterial agents as potential alternatives for addressing foodborne pathogens. Nowadays efforts are being made on exploring the potential of natural antibacterial agents against foodborne pathogens. In this study, the antibacterial efficacy of silver nanoparticles synthesized using S. polyanthum leaves extract (SP-AgNPs) against selected Gram-negative and Gram-positive foodborne pathogens was investigated by using multiple assays, including the well diffusion assay (WDA), minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill assay. The well diffusion assay demonstrated the inhibitory potential of SP-AgNPs against all tested foodborne pathogens, with inhibition zones ranging from 10.16 + 1.25 to 13.16 + 1.52 mm. Furthermore, the MIC values ranged from 0.008 to 0.125 mg/mL, indicating the potent antibacterial activity of SP-AgNPs across a broad spectrum of foodborne pathogens. The MBC values, ranging from 0.008 to 0.250 mg/mL, further confirming the bactericidal ability of SP-AgNPs against these pathogens. In the time-kill experiment, most foodborne pathogens were entirely killed after 4 h of incubation at 4 × MIC concentration. However, only E. coli, K. pneumoniae, and S. Typhimurium showed a reduction in population to 3 Log₁₀ CFU/mL, indicating a strong bactericidal effect of SP-AgNPs on most tested pathogens. In conclusion, this study provides compelling evidence that SP-AgNPs exhibit potent antibacterial activity against selected foodborne pathogens. The findings suggest that SP-AgNPs synthesized using S. polyanthum leaves extract hold great promise as a novel antibacterial agent for effectively controlling foodborne pathogens. These findings contribute to continuing efforts in developing alternative strategies to prevent foodborne diseases and enhance food safety.

Dry inoculation (DI) methods using a dry carrier have gained considerable interest for assessing thermal inactivation of Salmonella and other microorganisms in low-moisture foods. However,...

L. plantarum strains displayed different abilities to exhibit high survivability to acid (pH 3.0), bile salts (3%), enzyme (pepsin), and temperature (40 °C) and good antibiotic susceptibility. The isolates were further supplemented in traditional tapai pulut to study the immunomodulation properties of tapai pulut based on the splenic T- and B-cell populations. The mice groups were divided into group one (unfermented glutinous rice), group two (tapai pulut group), and group three (probiotic tapai pulut group). Group one showed consistent body weight gain, with the highest observed after four weeks. Group three exhibited the most significant reduction in the percentage of CD19+ B-cells. The CD3+ T-cells population of Group three increased significantly compared with the control mice, followed by Group two. The results suggest that traditional tapai pulut supplemented with L. plantarum has a high potential for supporting the immune system’s immunomodulatory effect.