Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a lactic acid bacteria species found on plants that is essential for many plant food fermentations. In this study, we investigated the intraspecific phenotypic and genetic diversity of 13 L. plantarum strains isolated from different plant foods, including fermented olives and tomatoes, cactus fruit, teff injera, wheat boza and wheat sourdough starter. We found that strains from the same or similar plant food types frequently exhibited similar carbohydrate metabolism and stress tolerance responses. The isolates from acidic, brine-containing ferments (olives and tomatoes) were more resistant to MRS adjusted to pH 3.5 or containing 4% w/v NaCl, than those recovered from grain fermentations. Strains from fermented olives grew robustly on raffinose as the sole carbon source and were better able to grow in the presence of ethanol (8% v/v or sequential exposure of 8% (v/v) and then 12% (v/v) ethanol) than most isolates from other plant types and the reference strain NCIMB8826R. Cell free culture supernatants from the olive-associated strains were also more effective at inhibiting growth of an olive spoilage strain of Saccharomyces cerevisiae. Multi-locus sequence typing and comparative genomics indicated that isolates from the same source tended to be genetically related. However, despite these similarities, other traits were highly variable between strains from the same plant source, including the capacity for biofilm formation and survival at pH 2 or 50°C. Genomic comparisons were unable to resolve strain differences, with the exception of the most phenotypically impaired and robust isolates, highlighting the importance of utilizing phenotypic studies to investigate differences between strains of L. plantarum. The findings show that L. plantarum is adapted for growth on specific plants or plant food types, but that intraspecific variation may be important for ecological fitness and strain coexistence within individual habitats.
Lactic acid bacteria have been isolated from living, harvested, and fermented plant materials; however, the adaptations these bacteria possess for growth on plant tissues are largely unknown. In this study, we investigated plant habitat-specific traits of Lactococcus lactis during growth in an Arabidopsis thaliana leaf tissue lysate (ATL). L. lactis KF147, a strain originally isolated from plants, exhibited a higher growth rate and reached 7.9-fold-greater cell densities during growth in ATL than the dairy-associated strain L. lactis IL1403. Transcriptome profiling (RNA-seq) of KF147 identified 853 induced and 264 repressed genes during growth in ATL compared to that in GM17 laboratory culture medium. Genes induced in ATL included those involved in the arginine deiminase pathway and a total of 140 carbohydrate transport and metabolism genes, many of which are involved in xylose, arabinose, cellobiose, and hemicellulose metabolism. The induction of those genes corresponded with L. lactis KF147 nutrient consumption and production of metabolic end products in ATL as measured by gas chromatography-time of flight mass spectrometry (GC-TOF/MS) untargeted metabolomic profiling. To assess the importance of specific plant-inducible genes for L. lactis growth in ATL, xylose metabolism was targeted for gene knockout mutagenesis. Wild-type L. lactis strain KF147 but not an xylA deletion mutant was able to grow using xylose as the sole carbon source. However, both strains grew to similarly high levels in ATL, indicating redundancy in L. lactis carbohydrate metabolism on plant tissues. These findings show that certain strains of L. lactis are well adapted for growth on plants and possess specific traits relevant for plant-based food, fuel, and feed fermentations. L actic acid bacteria (LAB) found on plants are essential for the production of a wide variety of plant-derived fermented foods with desirable organoleptic properties, improved nutritional attributes, and extended shelf life (1). LAB are a diverse group of bacterial species in the Firmicutes phylum that are characterized by the production of lactic acid as the main end product of carbohydrate metabolism. Some of the most commonly recognized genera among the LAB include Lactococcus, Lactobacillus, Leuconostoc, Pediococcus, and Oenococcus. LAB-fermented plantbased food products include sauerkraut, sourdough, and olives, as well as diverse foods unique to different ethnic groups (e.g., pulque, nukadoko, or gundruk [2,3]). LAB are responsible for the conversion of plant tissues such as alfalfa into silage for animal feed with enhanced nutritional content and stability (4). LAB are also used to ferment plant-based substrates into industrial-grade lactic acid for the manufacture of polylactide bioplastics (5). Conversely, LAB are frequent contaminants of bioethanol fermentations (6).In contrast to commercial dairy fermentations that utilize starter cultures, initiation of plant-based fermentations typically relies on the LAB that are located on or associated with plant tis...
Plantaricin EF (PlnEF) is a class IIb bacteriocin produced by Lactobacillus plantarum. We compared L. plantarum NCIMB8826 and LM0419, a plnEFI deletion mutant of that strain lacking plnEF and the gene for the cognate immunity protein plnI, in a 2,4,6-trinitrobenzenesulfonic acid (TNBS) induced mouse model of acute inflammatory bowel disease. Mice fed either L. plantarum NCIMB8826 or LM0419 were not protected against TNBS according to either disease activity or histology (Ameho) scores. Mice consuming NCIMB8826 exhibited intermediate (non-significant) levels of colonic tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) that ranged between the TNBS-treated animals and healthy controls. By comparison, TNF-α and IL-6 quantities were elevated in mice given L. plantarum LM0419 and equivalent to mice given TNBS alone. Both strains survived digestive tract transit in equal numbers and did not result in global changes to the bacterial composition in the intestine according to 16S rRNA gene sequencing either prior to or after TNBS administration. Examination of intestinal taxa showed that mice consuming wild-type L. plantarum, but not LM0419 contained lower proportions of Mucispirillum (Deferribacteres phylum) in the faeces prior to TNBS administration and Parabacteroides (Bacteroidetes phylum) in the caecum after disease induction. Parabacteroides also positively correlated with disease activity and histology scores. These findings suggest a role for PlnEFI production by L. plantarum in benefiting digestive tract health.
Chronic HIV infection results in impairment of gut-associated lymphoid tissue leading to systemic immune activation. We previously showed that in early SIV-infected rhesus macaques intestinal dysfunction is initiated with the induction of the IL-1β pathway in the small intestine and reversed by treatment with an exogenous Lactobacillus plantarum strain. Here, we provide evidence that the transcriptomes of L. plantarum and ileal microbiota are not altered shortly after SIV infection. L. plantarum adapts to the small intestine by expressing genes required for tolerating oxidative stress, modifying cell surface composition, and consumption of host glycans. The ileal microbiota of L. plantarum-containing healthy and SIV+ rhesus macaques also transcribed genes for host glycan metabolism as well as for cobalamin biosynthesis. Expression of these pathways by bacteria were proposed but not previously demonstrated in the mammalian small intestine.
Strains of Lactococcus lactis isolated from plant tissues possess adaptations that support their survival and growth in plant‐associated microbial habitats. We previously demonstrated that genes coding for a hybrid nonribosomal peptide synthetase/polyketide synthase (NRPS/PKS) system involved in production of an uncharacterized secondary metabolite are specifically induced in L. lactis KF147 during growth on plant tissues. Notably, this NRPS/PKS has only been identified in plant‐isolated strains of L. lactis. Here, we show that the L. lactis KF147 NRPS/PKS genes have homologs in certain Streptococcus mutans isolates and the genetic organization of the NRPS/PKS locus is conserved among L. lactis strains. Using an L. lactis KF147 mutant deficient in synthesis of NrpC, a 4′‐phosphopantetheinyl transferase, we found that the NRPS/PKS system improves L. lactis during growth under oxidative conditions in Arapidopsis thaliana leaf lysate. The NRPS/PKS system also improves tolerance of L. lactis to reactive oxygen species and specifically H2O2 and superoxide radicals in culture medium. These findings indicate that this secondary metabolite provides a novel mechanism for reactive oxygen species detoxification not previously known for this species.
The intraspecific phenotypic and genetic diversity of Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) was examined for five strains isolated from fermented olives and eight strains from cactus fruit, fermented tomatoes, teff injera, wheat boza, and wheat sourdough starter sources. Carbohydrate utilization and stress tolerance characteristics showed that the olive isolates grew more robustly in galactose and raffinose, showed higher tolerance to 12% v/v EtOH, and exhibited a greater capacity to inhibit an olive spoilage strain of Saccharomyces cerevisiae than L. plantarum from the other plant sources. Certain traits were variable between fermented olive isolates such as the capacity for biofilm formation and survival at pH 2 or 50 °C. By comparison, all L. plantarum from fruit sources grew better at a pH of 3.5 than the strains from fermented grains. Multi-locus sequence typing and genome sequencing indicated that strains from the same source type tended to be genetically related. Comparative genomics was unable to resolve strain differences, with the exception of the most phenotypically impaired and robust isolates. The findings show that L. plantarum is adapted for growth on specific plants or plant food types, but that intraspecific variation may be important for ecological fitness of L. plantarum within individual habitats.
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