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Several oral diseases are characterized by a shift within the oral microbiome towards a pathogenic, dysbiotic composition. Broad-spectrum antimicrobials are often part of patient care. However, because of the rising antibiotic resistance, alternatives are increasingly desirable. Alternatively, supplying beneficial species through probiotics is increasingly showing favorable results. Unfortunately, these probiotics are rarely evaluated comparatively. In this study, the in vitro effects of three known and three novel Lactobacillus strains, together with four novel Streptococcus salivarius strains were comparatively evaluated for antagonistic effects on proximal agar growth, antimicrobial properties of probiotic supernatant and the probiotic’s effects on in vitro periodontal biofilms. Strain-specific effects were observed as differences in efficacy between genera and differences within genera. While some of the Lactobacillus candidates were able to reduce the periodontal pathobiont A. actinomycetemcomitans, the S. salivarius strains were not. However, the S. salivarius strains were more effective against periodontal pathobionts P. intermedia, P. gingivalis, and F. nucleatum. Vexingly, most of the Lactobacillus strains also negatively affected the prevalence of commensal species within the biofilms, while this was lower for S. salivarius strains. Both within lactobacilli and streptococci, some strains showed significantly more inhibition of the pathobionts, indicating the importance of proper strain selection. Additionally, some species showed reductions in non-target species, which can result in unexpected and unexplored effects on the whole microbiome.

An expert panel was convened in September 2019 by The International Scientific Association for Probiotics and Prebiotics (ISAPP) to develop a definition for fermented foods and to describe their role in the human diet. Although these foods have been consumed for thousands of years, they are receiving increased attention among biologists, nutritionists, technologists, clinicians and consumers. Despite this interest, inconsistencies related to the use of the term ‘fermented’ led the panel to define fermented foods and beverages as “foods made through desired microbial growth and enzymatic conversions of food components”. This definition, encompassing the many varieties of fermented foods, is intended to clarify what is (and is not) a fermented food. The distinction between fermented foods and probiotics is further clarified. The panel also addressed the current state of knowledge on the safety, risks and health benefits, including an assessment of the nutritional attributes and a mechanistic rationale for how fermented foods could improve gastrointestinal and general health. The latest advancements in our understanding of the microbial ecology and systems biology of these foods were discussed. Finally, the panel reviewed how fermented foods are regulated and discussed efforts to include them as a separate category in national dietary guidelines., Although fermented foods have been consumed for thousands of years, a clear definition has been lacking. This Consensus Statement outlines a definition for the term ‘fermented foods’ as determined by an expert panel convened by the International Scientific Association for Probiotics and Prebiotics in September 2019.

In the original version of this Consensus Statement article published online, a bar in Figure 1 was incorrectly labelled as “parabiotics” when it should have been labelled as “paraprobiotics”. This error has now been corrected in the HTML and PDF version of the article. Figure 1 | Total number of mentions in the literature of different terms referring to inanimate microorganisms and/or their metabolites.

Endotoxins are components of Gram-negative bacteria with inherently high pro-inflammatory potential. In an urban environment, airborne endotoxins may associate with pollutants such as particulate matter, increasing the severity of the immune response by acting as a natural adjuvant to augment inflammatory respiratory disease development. Here, we present a closer look at outdoor urban endotoxins by applying a microbial-targeted collection strategy. Results from 87 samples distributed throughout the city of Antwerp ranged from 0.45 to 93.71 EU/m3, with a geometric mean of 4.49 EU/m3 and 95% confidence interval of 3.535.71 EU/m3. Sample collection was also coupled with the use of a Coulter counter, for which the particle count (2.510 μm/m3) showed a significant correlation with endotoxin concentration (R2 = 0.24; p

Lactobacilli have been evaluated as probiotics against Candida infections in several clinical trials, but with variable results. Predicting and understanding the clinical efficacy of Lactobacillus strains is hampered by an overall lack of insights into their modes of action. In this study, we aimed to unravel molecular mechanisms underlying the inhibitory effects of lactobacilli on hyphal morphogenesis, which is a crucial step in C. albicans virulence. Based on a screening of different Lactobacillus strains, we found that the closely related taxa L. rhamnosus, L. casei and L. paracasei showed stronger activity against Candida hyphae formation compared to other Lactobacillus species tested. By exploring the activity of purified compounds and mutants of the model strain L. rhamnosus GG, the major peptidoglycan hydrolase Msp1, conserved in the three closely related taxa, was identified as a key effector molecule. We could show that this activity of Msp1 was due to its ability to break down chitin, the main polymer in the hyphal cell wall of C. albicans. This identification of a Lactobacillus-specific protein with chitinase activity having anti-hyphal activity will assist in better strain selection and improved application in future clinical trials for Lactobacillus-based Candida-management strategies.

The knowledge of molecular mechanisms underlying the adhesive and mechanical properties of cell surface-associated molecules is a key to understanding their functions. In this context, single-molecule force spectroscopy (SMFS) has recently offered new opportunities for probing the adhesion and mechanics of polysaccharides and proteins on live cells. Here we present a protocol that we have used to analyze polysaccharide chains of different nature on the bacterium Lactobacillus rhamnosus GG. We describe procedures (i) for functionalizing atomic force microscopy (AFM) tips with Pseudomonas aeruginosa-I or concanavalin A lectins, (ii) for stretching specific polysaccharide molecules on live bacteria using SMFS with lectin tips and (iii) for mapping the localization, adhesion and extension of individual polysaccharide chains. We also discuss data treatment, emphasizing how to gain insight into the elasticity of the stretched macromolecules using the extended freely jointed chain model. Even though the presented protocol is for L. rhamnosus, it can be easily modified for other cell types. For users having expertise in the field, the entire protocol can be completed in about 5 d.

Background Bacterial interactions with the environment- and/or host largely depend on the bacterial glycome. The specificities of a bacterial glycome are largely determined by glycosyltransferases (GTs), the enzymes involved in transferring sugar moieties from an activated donor to a specific substrate. Of these GTs their coding regions, but mainly also their substrate specificity are still largely unannotated as most sequence-based annotation flows suffer from the lack of characterized sequence motifs that can aid in the prediction of the substrate specificity. Results In this work, we developed an analysis flow that uses sequence-based strategies to predict novel GTs, but also exploits a network-based approach to infer the putative substrate classes of these predicted GTs. Our analysis flow was benchmarked with the well-documented GT-repertoire of Campylobacter jejuni NCTC 11168 and applied to the probiotic model Lactobacillus rhamnosus GG to expand our insights in the glycosylation potential of this bacterium. In L. rhamnosus GG we could predict 48 GTs of which eight were not previously reported. For at least 20 of these GTs a substrate relation was inferred. Conclusions We confirmed through experimental validation our prediction of WelI acting upstream of WelE in the biosynthesis of exopolysaccharides. We further hypothesize to have identified in L. rhamnosus GG the yet undiscovered genes involved in the biosynthesis of glucose-rich glycans and novel GTs involved in the glycosylation of proteins. Interestingly, we also predict GTs with well-known functions in peptidoglycan synthesis to also play a role in protein glycosylation. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-349) contains supplementary material, which is available to authorized users.