Search

• B. subtilis postbiotics composition was modulated by MFG substrate size. • Energy-production cycle metabolites of bacteria grown on small MFG were elevated. • Metabolites that are used by the bacteria for biofilm formation were decreased when large MFG were used as a substrate. • Moderated response to LPS in MEC was documented when cells treated with small MFG postbiotics. Milk lipids are secreted into the milk collecting ducts as milk fat globule (MFG) where they are exposed to microflora of the udder. We hypothesized that MFG size modulates the metabolic fingerprint of B. subtilis. Accordingly, small and large (2.3 and 7.0 µm, respectively) MFG were isolated from cow milk and used as a substrate for B. subtilis. Small MFG enhanced growth, whereas large MFG enhanced biofilm formation. Bacteria incubated with small MFG had increased concentration of metabolites related to energy production whereas metabolome of the bacteria incubated with large MFG had reduced concentrations of metabolites important for biofilm formation. Postbiotics from bacteria grown on large MFG exacerbated the proinflammatory response of MEC to LPS, and changed the expression of key enzymes involved in lipid and protein synthesis. Our results suggest that MFG size modulate growth trajectories and metabolome of B. subtilis , and consequently the stress response of host cells. [ABSTRACT FROM AUTHOR]

Bacteria use different strategies to survive unfavorable environmental conditions. Alicyclobacillus acidoterrestris is a bacterium capable of surviving extremely harsh conditions, for instance, during industrial food processing. A. acidoterrestris is a spore-forming, thermoacidophilic, nonpathogenic bacterium that commonly contaminates commercial pasteurized fruit juices and is, therefore, considered a major microbiological contaminant in the juice industry. The purpose of this study was to elucidate whether A. acidoterrestris is capable of multicellular behavior by testing its ability of biofilm formation and surface motility. A. acidoterrestris was found to be proficient in migration over a surface that is apparently powered by flagella. It was further shown that lowering the external pH leads to inhibition in surface motility of these bacteria. Concomitantly, the reduction in the external pH triggered biofilm formation of A. acidoterrestris cells. Thus, although no significant biofilm was formed at pH 4.5, robust cell adhesion and confluent biofilm formation was seen below the pH 3.6. These findings indicate that the reduction of external pH is an environmental cue for the behavioral switch that inhibits surface motility and triggers biofilm formation of A. acidoterrestris. Gaining insight into the multicellular behavior that facilitates A. acidoterrestris survival in food contact surfaces may contribute to the development of novel antimicrobial means to prevent cross-contamination caused by this bacterium. [ABSTRACT FROM AUTHOR]

Abstract: Dental caries is one of the most common infectious diseases that affects humans. Streptococcus mutans, the main pathogenic bacterium associated with dental caries, produces a number of extracellular sucrose-metabolizing enzymes, such as glucosyltransferases (GTFB, GTFC and GTFD) and fructosyltransferase (FTF). The cooperative action of these enzymes is essential for sucrose-dependent cellular adhesion and biofilm formation. A global response regulator (vicR) plays important roles in S. mutans ftf and gtf expression in response to a variety of stimuli. A real-time reverse-transcription polymerase chain-reaction was used to quantify the relative levels of ftf, gtfB, gtfC, gtfD and vicR transcription of S. mutans in the presence of various dietary carbohydrates: sucrose, d-glucose, d-fructose, d-glucitol (d-sorbitol), d-mannitol and xylitol. Ftf was highly expressed at late exponential phase in the presence of sorbitol and mannitol. GtfB was highly expressed in the presence of all the above carbohydrates except for xylitol at early exponential growth phase and glucose and fructose at late exponential growth phase. Similar to gtfB, the expression of gtfC was also induced with the presence of all the tested carbohydrates except for xylitol at early growth and glucose and fructose at late exponential phase. In addition, no effect of mannitol on gtfC expression at early exponential phase was observed. GtfD was less influenced compared to the gtfB and gtfC, demonstrating enhanced expression especially in the presence of sorbitol, glucose, mannitol and xylitol at early exponential phase and mannitol at late exponential phase. VicR expression was induced only at the presence of xylitol at late exponential phase, and a decrease in expression was recorded at early exponential phase. Our findings show that dietary carbohydrates have a major influence on the transcription of ftf, gtfB, gtfC and gtfD, but less on vicR. Sorbitol and mannitol, which are considered as noncariogenic sugar substitutes, may indirectly affect caries by promoting biofilm formation via enhanced expression of gtfs and ftf. These results suggest regulatory circuits for exopolysaccharide gene expression in S. mutans. [Copyright &y& Elsevier]

Abstract: The extracellular enzyme fructosyltransferase (FTF) is considered to be a significant virulence factor in the dental biofilm. We have developed a method using surface plasmon resonance to detect the activity of immobilized FTF in situ. This real time technique provides a sensitive direct assay for characterizing functional properties of immobilized enzymes such as FTF. [Copyright &y& Elsevier]

The most cariogenic bacterium , Streptococcus mutans , often adopts a sessile lifestyle in response to carbohydrates. Biofilm formation represents one of the most successful strategies for survival by S. mutans in a dental environment. This study reports induced biofilm formation by S. mutans in the presence of lactose, the primary sugar in milk. Importantly, no major difference was observed in S. mutans growth in the presence of different concentrations of lactose in growth medium, indicating that lactose has a specific effect on biofilm formation. Moreover, extracellular polysaccharides produced by S. mutans in response to lactose were found to be different from the polysaccharides produced in the presence of sucrose. It is further reported that several biofilm-related genes of S. mutans were significantly up-regulated in response to lactose. These results lead to the conclusion that lactose may promote biofilm formation by S. mutans , the most important bacterium involved in dental diseases. [ABSTRACT FROM AUTHOR]

Sprouting seeds are considered part of a healthy and nutritious diet, and accordingly, their consumption increases globally. However, edible sprouts are occasionally linked to outbreaks of foodborne diseases, with Salmonella enterica being a frequent contaminant. Biocontrol was recently proposed as a possible approach to combat sprout contamination during production. The purpose of this study was to identify sprout-derived Salmonella -antagonists as a basis for the development of new biocontrol agents. To this end, spore-forming bacteria were isolated from sprouted mung bean seeds, based on either in vitro anti- Salmonella activity or rough colony morphology and tested in planta for inhibition of mung bean sprout colonization. Artificially contaminated seeds (2 log CFU/g) treated with selected Bacillus strains (7 log CFU/ml) demonstrated extensive inhibition of Salmonella growth after 4-days of sprouting, resulting in 3.3–5.4 log CFU/g reduction compared to control (untreated). The potent antagonistic activity of the selected Bacillus isolates was confirmed for different S. enterica serovars. Interestingly, some of the antagonistic strains that demonstrated activity in vitro were not active in planta and vice versa , indicating that in vitro testing may not be the best strategy for screening potential biocontrol strains in sprouts. Confocal microscopy imaging demonstrated that in the absence of Bacillus , Salmonella readily proliferates and colonizes the entire sprouting seed. Treatment with an antagonistic Bacillus isolate markedly inhibited the colonization of Salmonella. Scanning electron microscopy of Bacillus -treated sprouts demonstrated the colonization of the sprout with biofilm-like structures, indicating the activation of the biofilm formation mechanism during sprout colonization. The identified Bacillus isolates provide a basis for the future development of novel biocontrol agents against Salmonella and perhaps other foodborne pathogens in edible sprouts. • Bacillus strains from mung bean sprouts were screened for anti- Salmonella activity. • Selected isolates inhibited the colonization of Salmonella on sprouted bean seeds. • In vitro activity was not always correlated with biocontrol activity in the sprouts. • Bacillus strains may be used as biocontrol agents against Salmonella in sprouts. [ABSTRACT FROM AUTHOR]

Abstract: Bacillus species form biofilms within milking pipelines and on surfaces of equipment in the dairy industry which represent a continuous hygiene problem and can lead to serious economic losses due to food spoilage and equipment impairment. Although much is known about the mechanism by which the model organism Bacillus subtilis forms biofilms in laboratory mediums in vitro, little is known of how these biofilms are formed in natural environments such as milk. Besides, little is known of the signaling pathways leading to biofilm formation in other Bacillus species, such as Bacillus cereus and Bacillus licheniformis, both of which are known to contaminate milk. In this study, we report that milk triggers the formation of biofilm-related structures, termed bundles. We show this to be a conserved phenomenon among all Bacillus members tested. Moreover, we demonstrate that the tasA gene, which encodes a major portion of the matrix which holds the biofilm together, is vital for this process. Furthermore, we show that the free fatty acid (FFA) — butyric acid (BA), which is released during lipolysis of milk fat and demonstrates antimicrobial activity, is the potent trigger for biofilm bundle formation. We finally show that BA-triggered biofilm bundle formation is mediated by the histidine kinase, KinD. Taken together, these observations indicate that BA, which is a major FFA within milk triggers biofilm formation in a conserved mechanism among members of the Bacillus genus. [Copyright &y& Elsevier]

• Goats with free access to Pistacia lentiscus ingest ~144 gr/day tannins. • Goats fed on Pistacia lentiscus produced milk with higher protein and fat content. • Goats fed on Pistacia lentiscus produce milk with lower urea content and higher curd firmness. • Pistacia lentiscus increased omega 3 content and favorable ratio between Ω6/Ω3 FA in milk. We have previously shown that grazing in East-Mediterranean brushlands is associated with improved milk quality. However, grazing exposes animals to predation, heat stress, and parasites, and imposes labor constraint. In order to verify the hypothesis that feeding the tannin-rich browse species lentisk (Pistacia lentiscus L.) to confined dairy goats could serve as proxy to grazing in improving milk composition, 30 Damascus goats were assigned to 3 treatments for 3 weeks: goats were grazing for 4 h daily in Mediterranean brushland (treatment P) or were fed indoors with vetch hay without (H), or with (HPIS) lentisk foliage. Milk yield and dry matter intake were not affected by treatment. HPIS milk was richer in protein and milk-fat content than H milk. H milk had highest urea concentration, smallest milk-fat globules and highest phospholipid content (milk-fat basis). Curd firmness was 39 and 50% higher in the HPIS group, compared with P and H, respectively. HPIS milk had 39 and 90% higher n-3 fatty acids concentration than P and H, respectively. This study suggests that access to P. lentiscus intensifies the effect of grazing in Mediterranean woodland on milk composition. Thus, we present a nutritional strategy that not only retains the exceptional nutritional values and productivity of pasture feeding, but also participates in a profitable and sustainable agriculture with an emphasis on intensive ruminant animal-production systems. [ABSTRACT FROM AUTHOR]