Acetic acid bacteria, including the genera Acetobacter and Komagataeibacter, utilize phosphatidylcholine (PC) as a major membrane component, which plays an important role in their membrane physiology. However, the significance of PC abundance within the membrane remains speculative. Here, we constructed a mutant strain of A. pasteurianus through genome modification, enabling choline-dependent PC production. This mutant exhibited different dependencies on PC levels in response to strong and weak acid stress, requiring higher PC levels under strong acid stress but lower levels under weak acid stress. These findings provide new insights into the membrane-based mechanisms of acid-stress response in A. pasteurianus.

This study systematically elucidated the microbial community succession and functional gene dynamics during the postharvest spoilage process of Stropharia rugosoannulata by integrating physiological and biochemical indicators with metagenomic analysis. The experimental results demonstrated that as storage time extended, the activities of antioxidant enzymes (superoxide dismutase, peroxidase) in S. rugosoannulata significantly declined, while the content of membrane lipid peroxidation product malondialdehyde increased, leading to compromised cell membrane integrity and creating favorable conditions for microbial colonization. Metagenomic analysis revealed that during the spoilage phase (post-harvest day 14), the relative abundance of Pseudomonadota increased to 85.7%, with Pseudomonas replacing Ewingella as the absolutely dominant microbial population. Further functional gene analysis showed that the post-harvest day 14 exhibited significant enrichment of glycosyltransferases (GT0, GT1, GT2, GT4) and carbohydrate-binding modules (CBM10, CBM16, CBM50), along with pectinase (GH78), chitinase (GH19), and polysaccharide-modifying enzymes (CE4, CE11). This indicated a metabolic shift towards cell wall synthesis and substrate recognition. In contrast, the post-harvest day 7, prior to fruiting body softening, demonstrated high expression of glycoside hydrolases (GH1, GH2, GH4, GH94) and carbohydrate esterase CE8, focusing on the degradation of cellulose and starch. These findings, for the first time from a molecular ecology perspective, clarify that the essence of postharvest spoilage in S. rugosoannulata is a quality deterioration process driven by a Pseudomonas-dominated microbial community. The study provided a basis for the development of targeted antibacterial preservation strategies.

Lactic acid bacteria (LAB) are widely recognized for their health benefits and are commonly incorporated into functional foods. However, their survival and metabolic performance depend on the availability of appropriate substrates. This study evaluated the ability of LAB isolated from Dioscorea species to utilize starch from Dioscorea luzonensis, an endemic plant in the Philippines. Among the isolates tested, Limosilactobacillus fermentum PJG11 demonstrated the highest efficiency in converting D. luzonensis starch into glucose. This enhanced starch utilization can be explained by the upregulation of the α-amylase gene when the strain was cultured with its natural substrate, resulting in accelerated starch granule degradation. These findings underscore the importance of using natural, plant-derived substrates in the development of LAB-based functional foods to support optimal bacterial activity and improve carbohydrate breakdown for enhanced nutritional value.

Sanghuangporus baumii polysaccharides (SBP) are recognized for their valuable pharmacological activities, driving increasing interest in their medicinal potential. However, the biosynthetic pathway of SBP remains incompletely characterized. Phosphoglucose isomerase (PGI), a key enzyme in carbohydrate metabolism, catalyzes the reversible isomerization between glucose-6-phosphate (G-6-P) and fructose-6-phosphate (F-6-P) and is hypothesized to regulate polysaccharide biosynthesis in this fungus. In this study, the pgi gene from S. baumii (sbpgi) was cloned and created sbpgi-silenced mutants using RNA interference (RNAi) to investigate its function. Silencing sbpgi resulted in an approximately 20% reduction in mycelial biomass but concurrently enhanced the production of exopolysaccharide (EPS) and intracellular polysaccharide (IPS) by approximately 2.0-fold and 1.9-fold after 9 days, respectively. Furthermore, suppression of sbpgi expression markedly decreased the content of cell wall β-1,3-glucan (by ~23%) while increasing chitin deposition by about 1.7-fold, leading to alterations in cell wall architecture, including thickness, and changes in stress tolerance. Transcriptional analysis revealed that sbpgi silencing significantly upregulated the expression of key genes in the polysaccharide biosynthetic pathway, including ugpg and pmm, highlighting the critical regulatory role of sbpgi in polysaccharide production. Our findings provide a foundation for metabolic engineering strategies to develop high-yielding strains for the industrial production of SBP.

Water is indispensable to life, yet some cyanobacteria inhabit hyper-arid deserts and withstand complete desiccation. However, the molecular mechanisms enabling such acclimation remain incompletely understood. In Anabaena sp. strain PCC 7120, the gene avaKa, which encodes a protein of unknown function, has been shown to be required for desiccation tolerance. Here, we characterized the avaKa disruptant DRavaKa under dehydration-related stress conditions. DRavaKa displayed hypersensitivity to EDTA, and transcripts of iron-deficiency–inducible genes (isiA1, isiB, furA, and sufB) were elevated even in the absence of EDTA. Whole-cell absorption spectra of DRavaKa revealed a blue shift of the chlorophyll absorption peak, a characteristic feature of iron-deficient cyanobacteria. In addition, the oxidative-stress–inducible gene trxA2 was likewise upregulated. These results indicate that AvaKa contributes to iron homeostasis and that iron deficiency–induced oxidative stress likely underlies the dehydration sensitivity of DRavaKa.

Bacillus thuringiensis (Bt) has broad spectrum multipotent functionalities for pest and disease suppression, and growth promotion (PGP) of plants. Therefore, potency of 27 rice rhizospheric and 2 commercial Bt isolates was assessed for biocidal and PGP traits. Functionally rhizospheric Bts were broadly superior than commercial Bts. Virulence of the Bts varied against rice leaf folder (LF, Cnaphalocrocis medinalis) and stripe stem borer (SSB, Chilo suppresalis) larvae in laboratory, net house and field tests. Drosophila diet (DD) incorporation, cut leaf and field assays proved virulence of 5-9 Bt isolates against LF larvae with LC₅₀s 1.99 - 6.31 x 10⁸, 2.18 x 10⁶ - 2.25 x 10⁹ and 3.16 x 10⁶ – 1.25 x 10⁹ bacteria-spore-crystal (BSC)/ml, respectively, and TB261 was most (LC₅₀s 2.18 x 10⁶ – 3.98 x 10⁸ BSC/ml) infective. DD and cut stem assays for SSB proved virulence of 5 and 6 Bts with LC₅₀s 9.20 x 10⁶ - 3.62 x 10⁸ and 9.21 x 10⁶- 3.24 x 10⁸ BSC/ml, respectively, and maximum (LC₅₀s 9.20 – 9.21 x 10⁸ BSC/ml) infectivity of TB263. Eight Bts inhibited 1-4 out of 7 rice pathogens and 16 Bts antagonized 1-4 out of 9 entomopathogenic fungi. Biocidal principles of the Bts were cell wall/membrane hydrolyzing exoenzymes, toxin/inhibitors and crystal toxins. Furthermore, the Bts were also inhibited by 3 insecticides and 2 fungicides. The Bts possessed 1-4 PGP and phytostimulation traits also. The potent rhizospheric Bt can be prospected for overall improvement/sustenance of rice.