Intestinal commensal bacteria can inhibit dense colonization of the gut by vancomycin-resistant Enterococcus faecium (VRE), a leading cause of hospital-acquired infections
. A four-strained ...consortium of commensal bacteria that contains Blautia producta BP
can reverse antibiotic-induced susceptibility to VRE infection
. Here we show that BP
reduces growth of VRE by secreting a lantibiotic that is similar to the nisin-A produced by Lactococcus lactis. Although the growth of VRE is inhibited by BP
and L. lactis in vitro, only BP
colonizes the colon and reduces VRE density in vivo. In comparison to nisin-A, the BP
lantibiotic has reduced activity against intestinal commensal bacteria. In patients at high risk of VRE infection, high abundance of the lantibiotic gene is associated with reduced density of E. faecium. In germ-free mice transplanted with patient-derived faeces, resistance to VRE colonization correlates with abundance of the lantibiotic gene. Lantibiotic-producing commensal strains of the gastrointestinal tract reduce colonization by VRE and represent potential probiotic agents to re-establish resistance to VRE.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study ...simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UL, UM, UPUK
Lactococcus lactis subsp. lactis biovar diacetylactis strains are used in the dairy industry for generating acetoin and notably diacetyl which imparts a high level of buttery flavor notes.
A ...collection of domesticated and environmental strains was screened for the production of diacetyl or acetoin (D/A), and citrate fermentation. Unexpectedly, both domesticated and environmental strains produced D/A. Domesticated strains belonging to the currently named “biovar diacetylactis” metabolized citrate and produced large amounts of D/A during early growth. They harbored the citP plasmid gene encoding citrate permease and a chromosomal region citM-citI-citCDEFXG involved in citrate metabolism. In these strains, citrate consumption was identified as the major determinant of aroma production. Environmental strains, specifically UCMA5716 and A12, produced as much D/A as the CitP+ strains, though at slightly lower rates. UCMA5716 was found to contain the citM-citI-citCDEFXG cluster but not the citP gene. A12 had neither. In these strains, production rate of D/A was linearly correlated with pyruvate synthesis rate. However, the correlation factor was strain-dependent, suggesting different modes of regulation for pyruvate rerouting towards fermentation end-products and flavors.
This work highlights the genetic and metabolic differences between environmental and domesticated strains. The introduction of environmental strains into industrial processes could considerably increase the diversity of starters, enhancing the delivery of new technological properties.
► A collection of L. lactis subsp. lactis strains was screened for diacetyl/acetoin production. ► Whatever their origin, L. lactis subsp. lactis strains produce diacetyl/acetoin. ► Citrate pathway is the major determinant of rapid synthesis of acetoin. ► Production rate of acetoin is linearly correlated with pyruvate synthesis rate. ► This correlation is strain-dependent.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Designer microbial consortia are an emerging frontier in synthetic biology that enable versatile microbiome engineering. However, the utilization of such consortia is hindered by our limited capacity ...in rapidly creating ecosystems with desired dynamics. Here we present the development of synthetic communities through social interaction engineering that combines modular pathway reconfiguration with model creation. Specifically, we created six two-strain consortia, each possessing a unique mode of interaction, including commensalism, amensalism, neutralism, cooperation, competition and predation. These consortia follow distinct population dynamics with characteristics determined by the underlying interaction modes. We showed that models derived from two-strain consortia can be used to design three- and four-strain ecosystems with predictable behaviors and further extended to provide insights into community dynamics in space. This work sheds light on the organization of interacting microbial species and provides a systematic framework-social interaction programming-to guide the development of synthetic ecosystems for diverse purposes.
Lactococcus lactis is an organism of substantial economic importance, used extensively in the production of fermented foods and widely held to have evolved from plant strains. The domestication of ...this organism to the milk environment is associated with genome reduction and gene decay, and the acquisition of specific genes involved in protein and lactose utilisation by horizontal gene transfer. In recent years, numerous studies have focused on uncovering the physiology and molecular biology of lactococcal strains from the wider environment for exploitation in the dairy industry. This in turn has facilitated comparative genome analysis of lactococci from different environments and provided insight into the natural phenotypic and genetic diversity of L. lactis. This diversity may be exploited in dairy fermentations to develop products with improved quality and sensory attributes. In this review, we discuss the classification of L. lactis and the problems that arise with phenotype/genotype designation. We also discuss the adaptation of non-dairy lactococci to milk, the traits associated with this adaptation and the potential application of non-dairy lactococci to dairy fermentations.
•Lactococcus lactis inhabits in a wide range of environmental niches.•Due to phenotype–genotype mismatching, a complex taxonomical structure exists.•Adaptation to the milk environment has led to significant changes in the L. lactis genome.•Non-dairy lactococci may have beneficial applications in dairy fermentations.•Strains from non-dairy environments should be evaluated for safety for use in foods.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Bacterial group II introns are large catalytic RNAs related to nuclear spliceosomal introns and eukaryotic retrotransposons. They self-splice, yielding mature RNA, and integrate into DNA as ...retroelements. A fully active group II intron forms a ribonucleoprotein complex comprising the intron ribozyme and an intron-encoded protein that performs multiple activities including reverse transcription, in which intron RNA is copied into the DNA target. Here we report cryo-EM structures of an endogenously spliced Lactococcus lactis group IIA intron in its ribonucleoprotein complex form at 3.8-Å resolution and in its protein-depleted form at 4.5-Å resolution, revealing functional coordination of the intron RNA with the protein. Remarkably, the protein structure reveals a close relationship between the reverse transcriptase catalytic domain and telomerase, whereas the active splicing center resembles the spliceosomal Prp8 protein. These extraordinary similarities hint at intricate ancestral relationships and provide new insights into splicing and retromobility.
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IJS, NUK, SBMB, UL, UM, UPUK
Lactococcus lactis subsp. lactis BGMN1-5 produces a leaderless class II bacteriocin called LsbB. To identify the receptor for LsbB, a cosmid library of the LsbB-sensitive strain BGMN1-596 was ...constructed. About 150 cosmid clones were individually isolated and transferred to LsbB-resistant mutants of BGMN1-596. Cosmid pAZILcos/MN2, carrying a 40-kb insert, was found to restore LsbB sensitivity in LsbB-resistant mutants. Further subcloning revealed that a 1.9-kb fragment, containing only one open reading frame, was sufficient to restore sensitivity. The fragment contains the gene yvjB coding for a Zn-dependent membrane-bound metallopeptidase, suggesting that this gene may serve as the receptor for LsbB. Further support for this notion derives from several independent experiments: (i) whole-genome sequencing confirmed that all LsbB-resistant mutants contain mutations in yvjB; (ii) disruption of yvjB by direct gene knockout rendered sensitive strains BGMN1-596 and IL1403 resistant to LsbB; and (iii) most compellingly, heterologous expression of yvjB in naturally resistant strains of other species, such as Lactobacillus paracasei and Enterococcus faecalis, also rendered them sensitive to the bacteriocin. To our knowledge, this is the first time a membrane-bound peptidase gene has been shown to be involved in bacteriocin sensitivity in target cells. We also demonstrated a novel successful approach for identifying bacteriocin receptors.
•Trehalose ensures the highest survival of L. lactis during drying and storage at 20 °C.•Spray-drying is an attractive alternative to freeze-drying for properly protected cells.•Spray-dried cells ...protected with skimmed milk showed the highest resistance to simulated digestion.•Cells from spray-dried skimmed milk-protected preparation had the highest in vitro adhesion ability.
In order to assess the essential probiotic properties of a strain dedicated for administration in humans and animals, characteristics of finally formulated products, rather than the cells solely, seems to be of crucial importance. In this study, composition of protective blends for manufacture of L. lactis probiotic powders was optimized using a statistical experimental design. The powders, generated by either spray- or freeze-drying techniques, were subsequently subjected to storage testing, and in vitro digestion in simulated stomach and small intestine. Finally, maintenance of adherence capability to human enterocyte-like cell lines, was evaluated. Our data demonstrated that 10% trehalose ensures the highest viability of L. lactis bacteria upon both drying techniques (viability of 60–68%). Moreover, skimmed milk-protected spray-dried cells exhibit the highest resistance to harsh environmental conditions of stomach (53.9 ± 7.6% survival rate) and higher adhesion ability to HT-29 cell line after digestion (528 ± 29 cells per 100 epithelial cells).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lactococcus species are counted among a large and closely related group of environmental streptococci and streptococci-like bacteria that include bovine mastitis pathogenic Streptococcus, ...Enterococcus, and Aerococcus species. Phenotypic and biochemical identification methods can be inaccurate and unreliable for species within this group, particularly for Lactococcus spp. As a result, the incidence of Lactococcus spp. on the farm may have been historically underreported and consequently little is known about the clinical importance of this genus as a mastitis pathogen. We used molecular genetic identification methods to accurately differentiate 60 environmental streptococci and streptococci-like bacteria isolated from cows with high somatic cell count and chronic intramammary infection (IMI; >2 somatic cell scores above 4) among 5 geographically distinct farms in New York and Minnesota that exhibited an observed increase in IMI. These isolates were phenotypically identified as Streptococcus uberis and Streptococcus spp. Genetic methods identified 42 isolates (70%) as Lactococcus lactis ssp. lactis, including all 10 isolates originally phenotypically identified as Streptococcus uberis. Antibiotic inhibition testing of all Lc. lactis ssp. lactis showed that 7 isolates were resistant to tetracycline. In the present study, a predominance of Lc. lactis ssp. lactis was identified in association with chronic, clinical bovine IMI among all 5 farms and characterized antimicrobial resistance for treatment therapies. Routine use by mastitis testing labs of molecular identification methods for environmental streptococci and streptococci-like bacteria can further define the role and prevalence of Lc. lactis ssp. lactis in association with bovine IMI and may lead to more targeted therapies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Highlights • Food grade bacteria poses potential to remove heavy metals contamination. • Lactococcus lactis subsp . lactis with cadmium resistance was newly isolated. • Ultrastructural analysis ...reveals the cadmium tolerant properties. • Cadmium mainly accumulated in cell membrane structures. • OH and NH2 on cell surface structures play essential role in cadmium biosorption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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