Journal of Basic Microbiology最新文献

The textile industry releases large volumes of harmful chemicals, including residual dyes and xenobiotics—synthetic or foreign compounds not naturally produced or expected in living systems, such as dyes, surfactants, and pesticides. These pollutants contribute to environmental toxicity, mutagenicity, and carcinogenicity. While physicochemical treatments are commonly employed for dye and heavy metal removal, bioremediation using microorganisms offers a sustainable and eco-friendly alternative. Diverse microbial groups, including bacteria, fungi, and microalgae, can degrade textile pollutants through specialized metabolic pathways. However, biodegradation efficiency is often influenced by dye toxicity, environmental stress, and microbial diversity. Sulfate-reducing bacteria (SRBs) have emerged as promising agents for bioremediation due to their metabolic versatility. SRBs reduce sulfate to hydrogen sulfide (H₂S), which reacts with heavy metals to form insoluble metal sulfides, enabling their effective removal from wastewater. SRBs are also capable of decolourizing textile dyes—particularly azo dyes and, to a lesser extent, anthraquinone, triphenylmethane, and sulfur dyes—thereby enhancing their capacity for pollutant degradation and heavy metal removal. Understanding the role of SRBs requires a thorough knowledge of the sulfur cycle, including biogeochemical pathways, reduction mechanisms, and the genes and enzymes involved. Sulfur itself holds significant importance in agriculture and industry, further emphasizing the relevance of SRBs in environmental remediation. This review underscores the significance of sulfur, key features of the sulfur cycle, and the physiological roles of SRBs in degrading textile pollutants, positioning them as vital contributors to sustainable wastewater treatment strategies.

Successful colonization of plant roots is vital for optimizing rhizobacterial benefits, but osmotic stress can significantly impact bacterial colonization. In this study, mustard seedlings were grown under no stress and osmotic stress (20% PEG 6000) conditions, and root exudates (RE_C and RE_OS, respectively) were collected. We analyzed how osmotic stress alters root exudate metabolites, and their impact on motility, biofilm formation, hydrolytic enzyme production and changes in cell surface components of rhizobacteria Bacillus sp. MRD-17 and B. casamancensis MKS-6. Chemical analysis revealed that RE_OS contained higher levels of sugars, organic acids (salicylic and succinic), fatty acids (octadecanoic), and phenolics/flavonoids (quercetin, genistein, dihydrodaidzein). MKS-6 exhibited higher motility in medium supplemented with root exudates from osmotic-stressed plants (RE_OS) compared to control exudates (RE_C), whereas MRD-17 showed no significant motility towards root exudates but exhibited a larger colony diameter in RE_OS than RE_C. Both rhizobacteria formed biofilms and moved toward root exudates with higher cfu/mL in RE_OS. Osmotic stress and root exudates altered rhizobacterial cell surface components and significantly affected cell wall protein expression. Osmotic stress influenced the rhizobacterial production of cell-wall hydrolytic enzymes. Seedlings inoculated with the rhizobacteria showed increased defense enzyme activities (peroxidase and polyphenol oxidase). The changes in root exudate components were positively correlated with colonization parameters. These findings indicate that osmotic stress-induced modifications in mustard root exudates enhance colonization traits of the rhizobacteria, highlighting their potential for drought stress mitigation through bioformulation development.

Beauveria bassiana and Metarhizium rileyi are entomopathogenic fungi that are widely present in nature. Due to their excellent insecticidal activity, they have been widely developed as microbial preparations and utilized in the biological control of pests. To clarify differences in pathogenicity between B. bassiana and M. rileyi against Spodoptera frugiperda, third-instar larvae were subjected to immersion treatments, whereas fifth-instar larvae were inoculated via injection with various doses of fungal strains B. bassiana AJS91881 and M. rileyi SXBN200920. Our results demonstrated differential virulence between fungal species depending on the infection method. Specifically, in immersion assays, M. rileyi displayed significantly higher pathogenicity compared with B. bassiana. Survival assessments of mixed-infection groups (1:9, 1:1, and 9:1) revealed reduced larval LT₅₀ values corresponding to elevated proportions of M. rileyi. Conversely, B. bassiana exhibited significantly enhanced pathogenicity relative to M. rileyi in injection assays, with higher proportions of B. bassiana (9:1, 1:1, 1:9 groups) resulting in reduced LT₅₀ values. GM diversity analysis further illustrated distinct microbiota alterations correlated with varying fungal ratios. Divergent virulence observed between immersion and injection protocols likely stems from fundamentally different infection mechanisms employed by B. bassiana and M. rileyi. In vitro cultivation experiments demonstrated superior growth of B. bassiana compared to M. rileyi. Thus, B. bassiana was more pathogenic in intra-hemoceol injection bioassay, whereas M. rileyi demonstrated greater efficacy in immersion bioassay. Overall, this study provides preliminary evidence for differential pathogenicity mechanisms between B. bassiana and M. rileyi toward S. frugiperda larvae, contributing important knowledge for agricultural biocontrol programs.

Endophytes are a diverse group of microbes that colonize internal plant tissues without causing harm to the host. They play a crucial role in plant growth, development, and stress management. The is a complex mechanism involving evasive strategies to bypass host immune response, significant alteration in plant gene expression and establishment of a balance mutualistic relationship. Endophytes enhance plant health through various direct and indirect mechanisms, including the production of phytohormones such as auxin, gibberellins, and cytokinin. Moreover, they also solubilize nutrients, mainly nitrogen and phosphorus. A significant contribution of endophytes is the induction of induced systemic resistance (ISR), a defense response that primes the plant against a broad spectrum of pathogens and environmental stressors. The colonization of endophytes is governed by complex signaling pathways, immune modulation and tissue specificity, influenced by host genotype, age, and environmental conditions. This review highlights the ecological significance, mechanisms of colonization and functional contribution of endophytes to host plants. Furthermore, the review emphasizes that endophytes can recruit or influence other beneficial microbes in the rhizosphere region of host plants. Conclusively, this review synthesizes current understanding of the molecular strategies these microbes employ to survive within plant tissue and modulate plant immune system. We emphasize the immense, yet underexploited, potential of endophytes in enhancing plant resilience and productivity and advocates further research into their mechanisms and applications to meet growing demands of global agriculture.

Simple sequence repeats (SSRs) represent a fundamental component of an organism's genome and can play critical roles in genome organization and evolution. In this study, we examined the prevalence, relative abundance (RA), and relative density (RD) of long SSRs across various methanogens to uncover their evolutionary relevance and potential functional implications. Among the species analyzed, Methanococcus aeolicus exhibited the highest RA and RD values (110.0 and 1844.5, respectively), followed by Methanococcus liminatans (86.6 and 1087.0). In contrast, the lowest values were observed in Methanococcus abyssi (20.6 and 277.0). Notably, methanogens are generally characterized by A + T-rich genomes, and a positive correlation (r = 0.380) was found between SSR frequency and AT content. SSRs were distributed unevenly between genic and intergenic regions: on average, 65.4 SSRs (67.4% of total) were located in genic regions, while 31.6 SSRs (32.4%) occurred in intergenic regions. To explore potential functional effects of SSRs, we performed 3D structural modelling of a long-SSR-containing 4Fe–4S domain protein from Methanococcus maripaludis. The model revealed that SSR insertions may influence domain–domain interactions and modulate the accessibility and flexibility of the active site, potentially contributing to protein adaptation under stress conditions and during methane production.

Multispecies biofilms combining Anabaena torulosa (An) with Trichoderma viride (Tr) along with either Providencia sp. (PW5) or Pseudomonas nitroreducens (B3) were optimized using eleven treatments with different inoculation strategies and evaluated from liquid to soil mesocosms scales. The optimal treatment, An-Tr (7 days after inoculation (DAI)) + PW5 (9 DAI), demonstrated significant increases in chlorophyll (45.2%), indole-3-acetic acid (66.9%) and total sugars (24.76%) over An alone, in liquid mesocosm, along with the highest polysaccharide content (6.56 mg g soil⁻¹) in soil-based mesocosms. Under controlled flask-conditions, An-Tr (7 DAI) + PW5 (9 DAI) and An-Tr (7 DAI) + B3 (9 DAI) exhibited higher nitrate reductase (30.4% and 25.1%) and glutamine synthetase (36.9% and 36.6%) activities compared to An alone, accompanied by elevated proteins. In soil-based micro- and mesocosms, An-Tr (7 DAI) + PW5 (9 DAI) demonstrated superior colonization potential reflected as enhanced enzyme activities, with one-fold increase in the activity of soil urease, β-glucosidase and soil chlorophyll against uninoculated soil. Phospholipid fatty acid (PLFA) analysis revealed distinct profiles, An-Tr (7 DAI) + B3 (9 DAI) exhibited higher 18:1 w9c and MUFA markers, with increased microbial activity and Gram-negative bacteria and anaerobic populations. In contrast, An-Tr (7 DAI) + PW5 (9 DAI) profiles demonstrated higher Gram-positive bacterial population, indicating enhanced resilience and nutrient cycling capacity. These collective findings underscore the promise of tailored inoculation strategies in optimizing biofilm composition for multifunctionality.

Fenoxaprop-p-ethyl is a widely employed aryloxyphenoxypropionate herbicide that inhibits acetyl-CoA carboxylase (ACCase), thus interfering with fatty acid biosynthesis in target organisms. While its effects on terrestrial plants are well-documented, its impact on nontarget aquatic microorganisms, particularly cyanobacteria, which serve as the foundation of many aquatic ecosystems, remains inadequately characterized. Consequently, this study was undertaken to evaluate the differential uptake and metabolic responses of two cyanobacterial species, Anabaena laxa and Nostoc muscorum, upon exposure to fenoxaprop-p-ethyl. Cyanobacterial cultures were subjected to 200 mg/L of fenoxaprop-p-ethyl under controlled experimental conditions. Bioaccumulation was quantified, and a comprehensive analysis of photosynthetic parameters was conducted, including chlorophyll-a, carotenoids, CO₂ fixation, Rubisco, and PEPC activity. Additional biochemical profiling encompassed carbohydrates, organic acids, amino acids, and fatty acid composition. Anabaena exhibited a 26.3% higher accumulation of the herbicide compared to Nostoc (4.70 vs. 3.72 μg/g). Both species demonstrated substantial reductions in chlorophyll-a (57.4% in Anabaena, 47.2% in Nostoc) along with increased carotenoid production, with Nostoc displaying superior defensive capabilities (67.4% vs. 37.6% increase). Carboxylation enzyme activities were more severely inhibited in Anabaena. Despite ACCase inhibition, both species exhibited notable increases in total fatty acids, with distinct species-specific patterns in the accumulation of saturated, monounsaturated, and polyunsaturated fatty acids. Metabolic reconfiguration was further evidenced by significant accumulations of carbohydrates, organic acids, and selective amino acids, particularly branched-chain amino acids. The results highlight distinct species-specific metabolic adaptations to herbicide-induced stress, with Nostoc displaying more robust stress response mechanisms despite lower herbicide uptake. These findings provide valuable insights into the resilience of cyanobacteria to agrochemical exposure and underscore the potential ecological implications for aquatic microbial communities in agricultural watersheds.

Clostridium perfringens epsilon toxin (ETX) is a potent pore-forming exotoxin responsible for severe enterotoxemia and necrotizing enterocolitis in ruminants. To elucidate the molecular mechanisms underlying ETX pathogenicity and attenuation, several site-directed mutants (R25A, F92A, Y133A, F206A, D210A, and G221A) were constructed based on structural analysis. Cytotoxicity assays revealed reduced virulence in ETX-Y133A (hereafter referred to as Y133A), F92A, and F206A, with Y133A exhibiting the most significant attenuation. To further investigate the role of residue Y133, additional mutants (Y133E, Y133F, Y133S, Y133W, and Y133G) were generated. Selected mutants were evaluated for cytotoxicity, pathogenicity in BALB/c mice, and in vivo safety through histopathological analysis. Furthermore, their pore-forming ability, binding affinity to MDCK cells, and oligomerization properties were assessed. Results demonstrated that residue Y133 is critical for ETX activity, likely due to the necessity of its aromatic side chain for pore formation. In contrast, F92 and F206 appear to be involved in host–cell interactions via distinct mechanisms. These findings provide insights into ETX structure–function relationships and offer potential strategies for rational attenuation in vaccine development.