An overview on endophytic bacterial diversity habitat in vegetables and fruits

Characterization and efficacy of Salmonella phage cocktail PHA46 in the control of Salmonella Newport and Typhimurium internalized into cherry tomatoes

Non-typhoid Salmonella enterica causes salmonellosis illness, and this bacterium can contaminate food throughout the production chain, including those that are consumed as raw products. Salmonella enterica can adhere to and internalize into fresh produce such as cherry tomatoes. It has been reported that lytic bacteriophages (phages) can be used as a biocontrol agent in the agricultural field, being an alternative for the control of Salmonella in red meat, fish, lettuce, and cabbage. The aim of this study was to characterize the two phages present in the PHA46 cocktail to determine their morphology, genome, host range, and resistance to different temperatures and pHs values; and later evaluate their lytic activity to reduce the adherence to and internalization of Salmonella enterica serovars Newport and Typhimurium into cherry tomatoes. In addition, in this work, we also explored the effect of the PHA46 cocktail on the virulence of S. Newport-45 and S. Typhimurium SL1344, recovered from the interior of cherry tomatoes, on the lifespan of the animal model Caenorhabditis elegans. The nematode C. elegans, recently has been used to test the virulence of Salmonella and it is easy to maintain and work with in the laboratory. The results revealed that the morphology obtained by Transmission Electron Microscopy of two phages from the PHA46 cocktail correspond to a myovirus, the analyses of their genomes sequences did not report virulence or antimicrobial resistance genes. The PHA46 sample is specific for 33 different serovars from different Salmonella strains and shows stability at 7 °C and pH 6. Also, the PHA46 cocktail was effective in reducing the adherence of S. Newport-45 and S. Typhimurium SL1344 to cherry tomatoes, at an average of 0.9 log10, respectively. Regarding internalized bacteria, the reduction was at an average of 1.2 log10, of the serovars mentioned above. The lifespan experiments in C. elegans showed by itself, that the PHA46 cocktail was harmless to the nematode, and the virulence from both Salmonella strains grown in vitro is diminished in the presence of the PHA46 cocktail. In conclusion, these results showed that the PHA46 cocktail could be a good candidate to be used as a biocontrol agent against Salmonella enterica.

Development of Multifunctional Nanoencapsulated trans-Resveratrol/Chitosan Nutraceutical Edible Coating for Strawberry Preservation

Phytochemical nanoencapsulation for nutrient delivery and edible coatings for perishable food preservation are two emerging technologies. Leveraging the strong antimicrobial function of phytochemical nutrients, we propose convergent research to integrate the two technologies by embedding phytochemical-encapsulated nanoparticles in an edible coating on fresh fruits to achieve multiple functions. In particular, we report the study of an edible coating on strawberries that is composited of trans-resveratrol (R)-encapsulated nanoparticles (RNPs) embedded in a chitosan (CS) matrix. The biodegradable and biocompatible RNPs significantly increased the aqueous solubility of R by 150-fold and bioavailability by 3.5-fold after oral administration. Our results demonstrated the abilities of the RNP-embedded CS edible coating to diminish dehydration, prevent nutrient loss, inhibit microbe growth, increase nutraceutical value, preserve strawberry quality, and extend shelf life during storage at both 22 and 4 °C. Such a phytochemical nanoencapsulation-based edible coating is promising for the dual purposes of enhancing nutrient delivery and preserving perishable foods.

Reticulate evolution underlies synergistic trait formation in human communities

This paper investigates how reticulate evolution contributes to a better understanding of human sociocultural evolution in general, and community formation in particular. Reticulate evolution is evolution as it occurs by means of symbiosis, symbiogenesis, lateral gene transfer, infective heredity, and hybridization. From these mechanisms and processes, we mainly zoom in on symbiosis and we investigate how it underlies the rise of (1) human, plant, animal, and machine interactions typical of agriculture, animal husbandry, farming, and industrialization; (2) diet-microbiome relationships; and (3) host-virome and other pathogen interactions that underlie human health and disease. We demonstrate that reticulate evolution necessitates an understanding of behavioral and cultural evolution at a community level, where reticulate causal processes underlie the rise of synergistic organizational traits.

Uncovering the diversity and contents of gene cassettes in class 1 integrons from the endophytes of raw vegetables

Rapid spread of antibiotic resistance genes (ARGs) in pathogens is threatening human health. Integrons allow bacteria to integrate and express foreign genes, facilitating horizontal transfer of ARGs in environments. Consumption of raw vegetables represents a pathway for human exposure to environmental ARGs. However, few studies have focused on integron-associated ARGs in the endophytes of raw vegetables. Here, based on the approach of qPCR and clone library, we quantified the abundance of integrase genes and analyzed the diversity and contents of resistance gene cassettes in class 1 integrons from the endophytes of six common raw vegetables. The results revealed that integrase genes for class 1 integron were most prevalent compared with class 2 and class 3 integron integrase genes (1-2 order magnitude, P < 0.05). The cucumber endophytes harbored a higher absolute abundance of integrase genes than other vegetables, while the highest bacterial abundance was detected in cabbage and cucumber endophytes. Thirty-two unique resistance gene cassettes were detected, the majority of which were associated with the genes encoding resistance to beta-lactam and aminoglycoside. Antibiotic resistance gene cassettes accounted for 52.5 % of the functionally annotated gene cassettes, and bla_TEM-157 and aadA2 were the most frequently detected resistance cassettes. Additionally, carrot endophytes harbored the highest proportion of antibiotic resistance gene cassettes in the class 1 integrons. Collectively, these results provide an in-depth view of acquired resistance genes by integrons in the raw vegetable endophytes and highlight the potential health risk of the transmission of ARGs via the food chain.

Analysis of Endophytic Bacterial Diversity From Different Dendrobium Stems and Discovery of an Endophyte Produced Dendrobine-Type Sesquiterpenoid Alkaloids

As the unique component of Dendrobium, dendrobine-type sesquiterpenoid alkaloids (DSAs) possess a variety of medicinal properties. It has been well documented that plant endophytes can in vitro synthesize secondary metabolites identical or similar to metabolites produced by their host plants. This study aimed to investigate the composition and distribution of endophytic bacteria of Dendrobium stems by Illumina MiSeq platform sequencing and cultivation-dependent methods and then to assess the potential for endophytic bacteria to produce DSAs. Results indicated that it was necessary to combine both cultivation-dependent and cultivation-independent methods to analyze the community structure of endophytic bacterial in plants comprehensively. The length of the Dendrobium stems influenced the endophytic bacterial community. The diversity and richness of endophytic bacteria in group J10_15cm of stems were the highest, which showed a significant difference from the other stem groups. However, there was no certain connection between the diversity and richness of endophytic bacteria and the content of dendrobine. It was most likely due to the influence of several specific endophytic bacteria genera, such as Sphingomonas and Rhodococcus. Athelia rolfsii, Myrothecium roridum, as pathogenic fungi, and Pectobacterium carotovorum subsp. actinidiae, as pathogenic bacteria of Dendrobium, were used to determine the antimicrobial activities. In these assays, six strains belonging to five genera showed antimicrobial activity against at least two phytopathogens. The strain BL-YJ10_15-29 (Paracoccus pueri THG-N2.35, 98.98%) showed the best antimicrobial activity against the three phytopathogens. In addition, 2 DSAs (6-hydroxydendrobine and nobilonine) were identified in the fermentation supernatant of the strain CM-YJ10_15-44 (Pseudomonas protegens CHA0, 99.24%), whereas the whole-genome analysis results further demonstrated that the precursors of the two DSAs [geranyl-PP and (E, E)-famesyl-PP] were synthesized mainly through the methyl-D-erythritol 4-phosphate pathway in this strain. This study provides new insight into the studies on the biosynthesis of DSAs and provides potential biocontrol bacteria.