Alanine and glutamate catabolism collaborate to ensure the success of Bacillus subtilis sporulation.

Sporulation as a typical bacterial differentiation process has been studied for decades. However, two crucial aspects of sporulation, (i) the energy sources supporting the process, and (ii) the maintenance of spore dormancy throughout sporulation, are scarcely explored. Here, we reported the crucial role of RocG-mediated glutamate catabolism in regulating mother cell lysis, a critical step for sporulation completion of Bacillus subtilis, likely by providing energy metabolite ATP. Notably, rocG overexpression resulted in an excessive ATP accumulation in sporulating cells, leading to adverse effects on future spore properties, e.g. increased germination efficiency, reduced DPA content, and lowered heat resistance. Additionally, we revealed that Ald-mediated alanine metabolism was highly related to the inhibition of premature germination and the maintenance of spore dormancy during sporulation, which might be achieved by decreasing the typical germinant L-alanine concentration in sporulating environment. Our data inferred that sporulation of B. subtilis was a highly orchestrated biological process requiring a delicate balance in diverse metabolic pathways, hence ensuring both the completion of sporulation and production of high-quality spores.

The underlying mechanism of bacterial spore germination: An update review.

Bacterial spores are highly resilient and universally present on earth and can irreversibly enter the food chain to cause food spoilage or foodborne illness once revived to resume vegetative growth. Traditionally, extensive thermal processing has been employed to efficiently kill spores; however, the relatively high thermal load adversely affects food quality attributes. In recent years, the germination-inactivation strategy has been developed to mildly kill spores based on the circumstance that germination can decrease spore-resilient properties. However, the failure to induce all spores to geminate, mainly owing to the heterogeneous germination behavior of spores, hampers the success of applying this strategy in the food industry. Undoubtedly, elucidating the detailed germination pathway and underlying mechanism can fill the gap in our understanding of germination heterogeneity, thereby facilitating the development of full-scale germination regimes to mildly kill spores. In this review, we comprehensively discuss the mechanisms of spore germination of Bacillus and Clostridium species, and update the molecular basis of the early germination events, for example, the activation of germination receptors, ion release, Ca-DPA release, and molecular events, combined with the latest research evidence. Moreover, high hydrostatic pressure (HHP), an advanced non-thermal food processing technology, can also trigger spore germination, providing a basis for the application of a germination-inactivation strategy in HHP processing. Here, we also summarize the diverse germination behaviors and mechanisms of spores of Bacillus and Clostridium species under HHP, with the aim of facilitating HHP as a mild processing technology with possible applications in food sterilization. Practical Application: This work provides fundamental basis for developing efficient killing strategies of bacterial spores in food industry.

Nanotubes fabricated from a triple helix polysaccharide as a novel carrier delivering doxorubicin for breast cancer therapy.

Most current strategies of drug delivery systems face momentous challenges owing to obvious biological barriers. It is urgently necessary to develop artificial nanocarriers with biological and physical properties to reduce the severe system cytotoxicity of chemical drugs. Herein, triggered by the stiffness and amphiphilicity of the triple helix ß-glucan (LNT), we developed a novel nanocarrier with the hydrophobic cavity for delivering the anti-cancer drug of doxorubicin. In our findings, based on the law of minimum surface energy, LNT with considerable chain stiffness self-assembled into nanotubes (LNT-NT) with the controlled hydrophobic nanotube diameter at the nanometer level positively depending on the molecular weight through hydrogen bonding and hydrophobic interaction in manners of "shoulder-to-shoulder" and "head-to-head" arrangements. The hydrophobic drug of doxorubicin was then demonstrated to be entrapped into LNT-NT through hydrophobic interaction. Doxorubicin loaded into LNT-NT nanocarriers significantly inhibited tumor growth in vitro and in vivo by promoting tumor cell apoptosis and blocking cell proliferation, showing a higher therapeutic efficacy of 74.5 % and less adverse effects than the free doxorubicin, which was ascribed to the enhanced targetability by LNT-NT. In conclusion, this work proposes an alternative strategy for delivering hydrophobic drugs to reduce cytotoxicity and enhance therapeutic effectiveness by constructing ß-glucan-based nanotubes as a promising nanocarrier.

Natural polysaccharides with different conformations: extraction, structure and anti-tumor activity.

Natural polysaccharides as sustainable polymers are rich sources with good biological safety and various biological functions, which are important research topics in the fields of food and medicine. However, their widespread medical application is hindered due to the technical difficulties in the extraction/purification and chain structure characterization of polysaccharides, as well as due to the lack of thorough understanding of the macromolecular chain conformation and the mechanism of bioaction for these polysaccharides. To provide a relatively comprehensive reference for relevant researchers, we mainly introduce several natural polysaccharides with different chain conformations including random coil, hyperbranched sphere, and triple helix in solution, as well as summarize their extraction and purification processes, characterization of chemical structure and chain conformation, anti-tumor activities and potential mechanisms.

Probiotic Yogurt Fortified with Chickpea Flour: Physico-Chemical Properties and Probiotic Survival during Storage and Simulated Gastrointestinal Transit.

In the present study, probiotic yogurt with Lactobacillus acidophilus LA5 and Bifidobacterium BB12 was produced via fortification with chickpea flour (0, 1, 2.5, 5% w/v). During refrigerated storage for five weeks, probiotics maintained a viable count above the minimum therapeutic level (106 CFU/g) in all yogurt types. Although there was no significant (p > 0.05) positive effect of chickpea flour on probiotic viability during storage, the addition of chickpea flour has beneficial effects on the viability of both probiotic species in the presence of gastric and intestinal juices, with 0.3% bile. This study also evaluated the physio-chemical properties of probiotic yogurt during storage. Some physicochemical properties of yogurt, such as water holding capacity and susceptibility to syneresis, were enhanced by the addition of chickpea flour. Hence, chickpea flour could be an attractive pulse ingredient in the production of probiotic yogurts for health-conscious consumers.

Recent Advances in Chain Conformation and Bioactivities of Triple-Helix Polysaccharides.

Natural polysaccharides derived from renewable biomass sources are regarded as environmentally friendly and sustainable polymers. As the third most abundant biomacromolecule in nature, after proteins and nucleic acids, polysaccharides are also closely related with many different life activities. In particular, ß-glucans are one of the most widely reported bioactive polysaccharides and are usually considered as biological response modifiers. Among them, ß-glucans with triple-helix conformation have been the hottest and most well-researched polysaccharides at present, especially lentinan and schizophyllan, which are clinically used as cancer therapies in some Asian countries. Thus, creation of these active triple-helix polysaccharides is beneficial to the research and development of sustainable "green" biopolymers in the fields of food and life sciences. Therefore, full fundamental research of triple-helix polysaccharides is essential to discover more applications for polysaccharides. In this Review, the recent research progress of chain conformations, bioactivities, and structure-function relationships of triple-helix ß-glucans is summarized. The main contents include the characterization methods of the macromolecular conformation, proof of triple helices, bioactivities, and structure-function relationships. We believe that the governments, enterprises, universities, and institutes dealing with the survival and health of human beings can expect the development of natural bioproducts in the future. Hence, a deep understanding of ß-glucans with triple-helix chain conformation is necessary for application of natural medicines and biologics for a sustainable world.