Biodiversity and technological features of Weissella isolates obtained from Brazilian artisanal cheese-producing regions

Comparative transcriptomic analysis reveals a potential link between sugar transporters and the diauxic growth of Weissella paramesenteroides YT175 on inulin

Inulin, a health-promoting dietary fiber, is efficiently metabolized by Weissella paramesenteroides YT175, a beneficial bacterium. The strain demonstrated a diauxic growth pattern within 48 h, reaching an optical density at 600 nm (OD600 nm) of approximately 1.5, accompanied by a significant decrease in pH to around 4.90. Thin-layer chromatography (TLC) analysis reveals an initial preference for inulin oligomers with lower degrees of polymerization (DP). Genomic sequence analysis identified a gene cluster, the pts1BCA operon, associated with inulin metabolism, which includes genes encoding sugar transport proteins, a beta-fructofuranosidase enzyme belonging to the glycoside hydrolase family 32 (GH32), and a transcriptional regulator. Comparative transcriptomic analysis revealed significant upregulation of genes encoding beta-fructofuranosidase, phosphotransferase system (PTS), major facilitator superfamily (MFS), and ATP-binding cassette (ABC) transporters, with qRT-PCR results validating the RNA-Seq data, underscoring their involvement in inulin metabolism. These findings propose a metabolic pathway for the strategic utilization of inulin by YT175, highlighting the synergistic role of its three types of membrane transport proteins in the consumption of inulin oligomers with diverse DPs and its diauxic growth behavior. These insights enhance our understanding of the interaction between probiotics and dietary fibers and pave the way for the development of novel synbiotic foods.

Profiling the gut structure and microbiota, and identifying two dominant bacteria belonging to the Weissella genus in mandarin fish (Siniperca chuatsi) fed an artificial diet

Mandarin fish (Siniperca chuatsi) fed with an artificial diet is progressively gaining popularity, which is important for reducing product prices and resource consumption. However, food is the decisive factor of intestinal microbes, and the profound effects of change in their feeding habit on intestinal microbes of mandarin fish have not been revealed. In the present study, live bait fish and artificial diet were used to feed mandarin fish for 8 weeks to study the effect of different feeding habits on the histology, microbiota structure and dominant bacteria of gut in mandarin fish. The results indicated that feeding with the artificial diet significantly increased the intestinal villi height and muscular thickness in the hindgut of mandarin fish. In addition, the microbiota results showed that there were significant differences of beta diversity of gut microbiota in mandarin fish fed with different diets. At the genus level, feeding artificial diets significantly increased the abundance of Weissella in the mandarin fish gut. Furthermore, two Weissella bacteria were identified and characterized from the midgut contents of mandarin fish fed with artificial diet. Based on 16S rRNA gene sequencing, nine strains were assigned as Weissella confusa (RM125), and one as Weissella cibaria (SJ548). Biochemical analyses based on the VITEK2 method revealed a pattern of metabolic activities against W. confusa RM125 and W. cibaria SJ548, with 13 positive and 29 negative results, respectively. W. confusa RM125 and W. cibaria SJ548 exhibited sensitivities toward a variety of pathogens, including V. harveyi, S. aureus and V. parahaemolyticus, E. coli, A. hydrophila, S. enterica, V. anguillarum, and V. alginolyticus, indicating potential probiotics. Therefore, our results confirmed that the transformation of feeding habit altered the structure, microbial composition and dominant bacteria in gut of mandarin fish, and provided evidence that Weissella might play a crucial role in the digestion and absorption of artificial diet in mandarin fish.

Smoked sausages of bovine meat produced in North Macedonia as a source of pro-technological lactic acid bacteria and coagulase-negative cocci

Smoked bovine sausages, traditional meat products from the Balkan Peninsula, are rich in microbial diversity and represent potential sources of pro-technological microorganisms. This study aimed to characterize these sausages from three different producers collected in green markets of North Macedonia. The analyses included physico-chemical (proximate composition, pH, aw), morpho-textural (color and texture), and microbiological assessments (viable plate counts). Moreover, an isolation campaign was conducted to identify and characterize pro-technological microorganisms. Significant variability was observed in moisture content (ranging from 33.70 to 48.61 %), hardness, and color among samples from different producers. Samples from producer 2 showed the lowest pH (mean ∼4.90) and the highest loads of lactic acid bacteria (up to ∼9 log cfu g-1). Coagulase-negative cocci ranged between 4.84 and 7.47 log cfu g-1. No potential pathogenic bacteria were detected. A total of 30 isolates, primarily Latilactobacillus sakei, Staphylococcus equorum, and Staphylococcus casei, were identified. Isolates of L. sakei S7, S13, and S27 showed strong in-vitro acidification performance, together with the production of exopolysaccharides (EPS), and protease activity. S. equorum isolates S1 and S2 exhibited protease and lipase activities, while isolates S. casei S21 and S28 showed notable lipase and protease activities, along with the production of EPS. Additionally, all S. equorum isolates, except S2, showed nitrate reductase activity, one of the key features able to affect sausage color. These findings highlighted the pro-technological traits of these microbial isolates, suggesting their potential use as starter or adjunct cultures in the meat industry to enhance product quality and safety.

Assessment of safety and in situ antibacterial activity of Weissella cibaria strains isolated from dairy farms in Minas Gerais State, Brazil, for their food application

Weissella cibaria W21, W25, and W42 strains have previously been characterized for their antagonism against a range of foodborne pathogens. However, prior to their use as protective agents, further analyses such as their safety and in situ activity are needed. The safety of W. cibaria W21, W25, and W42 strains was predicted in silico and confirmed experimentally. Analyses of their genomes using appropriate software did not reveal any acquired antimicrobial resistance genes, nor mobile genetic elements (MGEs). The survival of each strain was determined in vitro under conditions mimicking the gastrointestinal tract (GIT). Thus, hemolysis analysis was performed using blood agar and the cytotoxicity assay was determined using a mixture of two cell lines (80% of Caco-2 and 20% of HT-29). We also performed the inflammation and anti-inflammation capabilities of these strains using the promonocytic human cell line U937. The Weissella strains were found to be haemolysis-negative and non-cytotoxic and did not induce any inflammation. Furthermore, these strains adhered tightly to intestinal Caco-2 cell-lines and exerted in situ anti-proliferative activity against methicillin-resistant Staphylococcus aureus (strain MRSA S1) and Escherichia coli 181, a colistin-resistant strain. However, the W. cibaria strains showed low survival rate under simulated GIT conditions in vitro. The unusual LAB-strains W. cibaria strains W21, W25, and W42 are safe and endowed with potent antibacterial activities. These strains are therefore good candidates for industrial applications. The results of this study provide a characterization and insights into Weissella strains, which are considered unusual LAB, but which prompt a growing interest in their bio-functional properties and their potential industrial applications.

Profile of lactic acid bacteria (MALDI-TOF-MS) and physico-chemical and microbiological characteristics of the raw milk and fresh artisanal cheese from Serra Geral, Minas Gerais, Brazil

Artisanal cheese from Serra Geral, Minas Gerais, Brazil, stands out for its cultural asset and socio-economic relevance. However, standards of identity and quality and the peculiar terroir associated with the edaphoclimatic conditions have not been established. Therefore, the production flow diagram and the physico-chemical and microbiological quality of the raw milk, pingo (natural starter culture), production benches, water and fresh cheese were investigated for the first time. In addition, lactic acid bacteria (LAB) from cheese and its production environment were identified by MALDI-TOF. For that, 12 cheese making facilities were selected. The raw milk and pingo showed adequate physico-chemical characteristics for cheesemaking; however, high microbial counts were found. In the water, total and thermotolerant coliforms were also identified. The fresh cheeses were classified as 'high moisture and fat' and 'soft mass'. Most physico-chemical parameters were satisfactory; however, there were high counts of total coliforms, Staphylococcus spp. and coagulase-positive staphylococci. There were high counts of LAB in the raw milk, pingo, bench surface and fresh cheese. A total of 84 microbial biotypes from MRS agar were isolated. Lactococcus lactis was the predominant LAB, followed by Lactococcus garvieae. Leuconostoc mesenteroides (benches), Leuconostoc pseudomesenteroides (fresh cheese), and Enterococcus faecium (pingo) were identified sporadically. These results indicate the risks to public health associated with the consumption of the fresh cheese, and measures to improve its safety are needed.

The Weissella and Periweissella genera: up-to-date taxonomy, ecology, safety, biotechnological, and probiotic potential

Bacteria belonging to the genera Weissella and Periweissella are lactic acid bacteria, which emerged in the last decades for their probiotic and biotechnological potential. In 2015, an article reviewing the scientific literature till that date on the taxonomy, ecology, and biotechnological potential of the Weissella genus was published. Since then, the number of studies on this genus has increased enormously, several novel species have been discovered, the taxonomy of the genus underwent changes and new insights into the safety, and biotechnological and probiotic potential of weissellas and periweissellas could be gained. Here, we provide an updated overview (from 2015 until today) of the taxonomy, ecology, safety, biotechnological, and probiotic potential of these lactic acid bacteria.

The Controversial Nature of Some Non-Starter Lactic Acid Bacteria Actively Participating in Cheese Ripening

This mini review deals with some controversial non-starter lactic acid bacteria (NSLAB) species known to be both human and animal pathogens but also health-promoting and probiotic. The focus is on Lactococcus garvieae, two Streptococcus species (S. uberis and S. parauberis), four Weissella species (W. hellenica, W. confusa, W. paramesenteroides, and W. cibaria), and Mammalicoccus sciuri, which worldwide, are often found within the microbiotas of different kinds of cheese, mainly traditional artisanal cheeses made from raw milk and/or relying on environmental bacteria for their ripening. Based on literature data, the virulence and health-promoting effects of these bacteria are examined, and some of the mechanisms of these actions are reviewed. Additionally, their possible roles in cheese ripening are also discussed. The analysis of the literature data available so far showed that, in general, the pathogenic and the beneficial strains, despite belonging to the same species, show somewhat different genetic constitutions. Yet, when the safety of a given strain is assessed, genomic analysis on its own is not enough, and a polyphasic approach including additional physiological and functional tests is needed.

A novel repeat sequence-based PCR (rep-PCR) using specific repeat sequences of Mycobacterium intracellulare as a DNA fingerprinting

Repetitive sequence-based PCR (rep-PCR) is a potential epidemiological technique that can provide high-throughput genotype fingerprints of heterogeneous Mycobacterium strains rapidly. Previously published rep-PCR primers, which are based on nucleotide sequences of Gram-negative bacteria may have low specificity for mycobacteria. Moreover, it was difficult to ensure the continuity of the study after the commercial rep-PCR kit was discontinued. Here, we designed a novel rep-PCR for Mycobacterium intracellulare, a major cause of nontuberculous mycobacterial pulmonary disease with frequent recurrence. We screened the 7,645 repeat sequences for 200 fragments from the genome of M. intracellulare ATCC 13950 in silico, finally generating five primers with more than 90% identity for a total of 226 loci in the genome. The five primers could make different band patterns depending on the genome of three different M. intracellulare strains using an in silico test. The novel rep-PCR with the five primers was conducted using 34 bacterial samples of 7 species containing 25 M. intracellulare clinical isolates, compared with previous published rep-PCRs. This shows distinguished patterns depending on species and blotting assay for 6 species implied the sequence specificity of the five primers. The Designed rep-PCR had a 95-98% of similarity value in the reproducibility test and showed 7 groups of fingerprints in M. intracellulare strains. Designed rep-PCR had a correlation value of 0.814 with VNTR, reference epidemiological method. This study provides a promising genotype fingerprinting method for tracing the recurrence of heterogeneous M. intracellulare.

Microbial Ecology of Sheep Milk, Artisanal Feta, and Kefalograviera Cheeses. Part II: Technological, Safety, and Probiotic Attributes of Lactic Acid Bacteria Isolates

The aim of the present study was to examine 189 LAB strains belonging to the species Enterococcus faecium, E. faecalis, Lactococcus lactis, Pediococcus pentosaceus, Leuconostoc mesenteroides, Lactiplantibacillus pentosus, Latilactobacillus curvatus, Lp. plantarum, Levilactobacillus brevis, and Weissella paramesenteroides isolated form sheep milk, Feta and Kefalograviera cheeses at different ripening stages, for their technological compatibility with dairy products manufacturing, their activities that may compromise safety of the dairy products as well as their capacity to survive in the human gastrointestinal tract. For that purpose, milk acidification and coagulation capacity, caseinolytic, lipolytic, hemolytic, gelatinolytic, and bile salt hydrolase activity, production of exopolysaccharides, antimicrobial compounds, and biogenic amines, as well as acid and bile salt tolerance and antibiotic susceptibility were examined. The faster acidifying strains were Lc. lactis DRD 2658 and P. pentosaceus DRD 2657 that reduced the pH value of skim milk, within 6 h to 5.97 and 5.92, respectively. Strains able to perform weak caseinolysis were detected in all species assessed. On the contrary, lipolytic activity, production of exopolysaccharides, amino acid decarboxylation, hemolytic, gelatinase, and bile salt hydrolase activity were not detected. Variable susceptibility to the antibiotics examined was detected among LAB strains. However, in the majority of the cases, resistance was evident. None of the strains assessed, managed to survive to exposure at pH value 1. On the contrary, 25.9 and 88.9% of the strains survived after exposure at pH values 2 and 3, respectively; the reduction of the population was larger in the first case. The strains survived well after exposure to bile salts. The strain-dependent character of the properties examined was verified. Many strains, belonging to different species, have presented very interesting properties; however, further examination is needed before their potential use as starter or adjunct cultures.

Genomic Analyses of Weissella cibaria W25, a Potential Bacteriocin-Producing Strain Isolated from Pasture in Campos das Vertentes, Minas Gerais, Brazil

Weissella is a genus containing Gram-positive, heterofermentative bacteria belonging to the lactic acid bacteria (LAB) group. These bacteria are endowed with promising technological and antimicrobial attributes. Weissella cibaria W25 was isolated from a dairy environment where raw milk cheeses are produced. Therefore, we sequenced and assembled the W25 draft genome sequence, which consists of 41 contigs totaling ~2.4 Mbp, with a G + C content of 45.04%. Then we carried out a comprehensive comparative genomic analysis with W. cibaria 110, known to produce the weissellicin 110 bacteriocin, and four other non-bacteriocin-producing W. cibaria strains.