Biology subjects

Li, J. A.

Publications and source records attributed to Li, J. A..

4 recordsLinked to original sources

bioRxiv2026

Lactic acid bacterium Fructilactobacillus sanfranciscensis impairs fitness of yeast Maudiozyma humilis in synthetic wheat sourdough

Sourdough starters contain simple microbial communities typically consisting of a few bacterial species and one or two yeast species. The yeast Maudiozyma humilis and the lactic acid bacterium Fructilactobacillus sanfranciscensis often co-occur in sourdough starters and have been presumed to exist in a trophic relationship supported by glucose cross-feeding. However, previous research has highlighted a lack of evidence showing that yeast strains consume the glucose that F. sanfranciscensis produces. We have investigated the interaction between sourdough isolates of M. humilis and F. sanfranciscensis in a synthetic wheat sourdough medium, allowing us to control substrate composition and use flow cytometry to enumerate living and dead cells. M. humilis fitness was found to be lower in co-culture with F. sanfranciscensis than when grown alone. Analysis of spent medium composition highlighted the reliance of M. humilis on glucose rather than maltose for growth. Comparisons of predicted and measured co-culture metabolite content also revealed that F. sanfranciscensis consumed less maltose in co-culture than when grown alone. For the first time, we examined potential amino acid cross-feeding between M. humilis and F. sanfranciscensis, and found that within the pairing, F. sanfranciscensis was the main producer of amino acids. Our findings suggest that the M. humilis-F. sanfranciscensis interaction is likely to be neutral, or even competitive, with the strain identity of F. sanfranciscensis playing a defining role in the observed dominance of the bacteria and spent medium metabolite composition. ImportanceThe association of the yeast Maudiozyma humilis and the bacterium Fructilactobacillus sanfranciscensis in sourdough starters is well-documented, and together this pairing makes key functional and organoleptic contributions to the final bread product. Their relationship has historically been thought to be stabilised by cross-feeding of glucose to M. humilis. However, this theory has been drawn into question by recent research which found no evidence that M. humilis consumes the glucose produced by F. sanfranciscensis. Our understanding of cooperation, coexistence, and competition in microbial consortia affects approaches to ecosystem management in a broad variety of applied fields. The significance of our research is in demonstrating that this pairing does not interact mutualistically within a specified setting, providing support for neutral or competitive interactions as drivers of ecological stability.

microbiology↗

bioRxiv2024

Applying deconstructed sourdough communities and fermentation parameters to low-FODMAP wheat bread production

Despite being made with the same starting materials, standard and sourdough bread differ in terms of levels of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs). This study aims to assess the impact of a selected yeast-bacteria co-culture isolated from sourdough starters in conjunction with varying bread-making process parameters on bread FODMAP content and overall quality. A survey of the microbial composition of sourdough starters found that many contain Maudiozyma humilis and Fructilactobacillus sanfranciscensis. A selected pairing was used for small-scale bread-making, and dough fermentation and bread quality parameters were assessed. The sourdough microbes exerted distinctive effects on dough gassing capacity and FODMAP composition in comparison to bakers yeast. To meet low-FODMAP cutoff values, the presence of a fermenting yeast and an extended dough fermentation time (> 6 h) were necessary. Sensory panellists preferred the sourdough co-culture bread fermented for 24 h over the 6 h treatment, and detected more complex aromas in the former. An extended, low-temperature dough fermentation regimen can be used to produce low-FODMAP bread with standard bread-making materials, and the use of sourdough fermentation microbes confers distinct textural and organoleptic properties.

microbiology↗

bioRxiv2022

Tuft cells mediate commensal remodeling of the small intestinal antimicrobial landscape

Succinate produced by the commensal protist Tritrichomonas musculis (T. mu) stimulates chemosensory tuft cells, resulting in intestinal type 2 immunity. Tuft cells express the succinate receptor SUCNR1, yet this receptor does not mediate anti-helminth immunity nor alter protist colonization. Here, we report that microbial-derived succinate increases Paneth cell numbers and profoundly alters the antimicrobial peptide (AMP) landscape in the small intestine. Succinate was sufficient to drive this epithelial remodeling, but not in mice lacking tuft cell chemosensory components required to detect this metabolite. Tuft cells respond to succinate by stimulating type 2 immunity, leading to interleukin-13-mediated epithelial and AMP expression changes. Moreover, type 2 immunity decreases the total number of mucosa-associated bacteria and alters the small intestinal microbiota composition. These findings demonstrate that a single metabolite produced by commensals, like T. mu, can markedly shift the intestinal AMP profile and suggest that tuft cells utilize SUCNR1 to modulate bacterial homeostasis.

microbiology↗

bioRxiv2022

Metabolic diversity in commensal protists regulates intestinal immunity and trans-kingdom competition

The microbiota influences intestinal health and physiology, yet the contributions of commensal protists to the gut environment have been largely overlooked. Here, we identified several new rodent- and human-associated parabasalid protists. Genomic and metabolomic analyses of murine parabasalids from the genus Tritrichomonas revealed species-level differences in the excretion of the metabolite succinate. This metabolic dissimilarity results in distinct small intestinal immune responses during protist colonization. Metabolic differences between Tritrichomonas species also determine their ecological niche within the microbiota. By manipulating dietary fibers and developing in vitro protist culture, we show that different parabasalid species preferentially rely on dietary polysaccharides or mucus glycans. These polysaccharide preferences create trans-kingdom competition with specific commensal bacteria, which affects intestinal immunity in a diet-dependent manner. Our findings reveal unappreciated diversity in commensal parabasalids, elucidate differences in commensal protist metabolism, and suggest how dietary interventions could regulate their impact on gut health.

microbiology↗