Flagellar Assembly Research Articles

Environmental Stability Determines the Cytotoxicity of Metal-Organic Frameworks to a Nitrogen-Fixing Bacterium Azotobacter vinelandii.

During widespread applications of metal-organic frameworks (MOFs), the environmental hazards and risks of MOFs have aroused great concerns. In this study, we aimed to reveal the importance of the environmental stability of MOFs on their toxicity. Two Zn-MOFs, namely, ZIF-8 with high aqueous stability and Zn-BDC with low aqueous stability, were compared directly in the toxicological evaluations of a nitrogen-fixing bacterium Azotobacter vinelandii. Zn-BDC showed strong cytotoxicity at 100 mg/L and higher, inducing growth inhibition, cell apoptosis, structural changes, oxidative damage, and, consequently, loss of nitrogen fixation ability. In contrast, ZIF-8 was nearly nontoxic to A. vinelandii. The transcriptome analysis showed that Zn-BDC directly disturbed the ribosome pathway and lowered the expression level of nitrogen-fixing nif cluster genes. On the other hand, ZIF-8 stress could regulate the flagellar assembly, siderophore group nonribosomal peptide biosynthesis, bacterial chemotaxis, and amino sugar and nucleotide sugar metabolism pathways to promote the cell growth of A. vinelandii. Beyond that, the toxicity of Zn-MOFs to A. vinelandii was associated with the release of Zn2+, but Zn-MOFs were less toxic than the mixtures of their starting materials. Overall, our results suggested that the environmental stability of Zn-MOFs determined their environmental toxicity through different molecular pathways. Designing stable MOFs is preferred due to environment-friendly considerations.

Improvement of uranium adsorption in Kocuria rosea by phosphate: A combined physiological and proteomic analysis

In this study, a combined physiological and proteomic analysis was performed to investigate the effect of phosphate addition on uranium adsorption response of Kocuria rosea. When 0.4–5 g/L KH2PO4 was added to the culture medium, there was no significant change in biomass compared with the control (without KH2PO4 addition). Subsequently, the cells were collected and interacted with uranium solution (300 mg/L, 20 mL), and the adsorption rate of uranium was significantly increased from 22.14 % to 65.32 % with 3.0 g/L KH2PO4 addition. Meanwhile, the cells could release more phosphorus-containing substances and form thin film like uranium precipitates on the cell surface by fourier transform infrared spectroscopy and scanning electron microscopy characterization analyses. Furthermore, a proteomic approach was employed to reveal the regulation mechanism of phosphate on uranium interaction in the K. rosea cells. The bioinformatics analysis revealed that the differentially abundant proteins in K. rosea were mainly involved in cell motility, ribosomes, structural molecule activity, flagellar assembly, and energy metabolism under uranium stress. Interestingly, up-regulated proteins were significantly enriched for organic acid biosynthetic process in the cells with KH2PO4 addition. In addition, KH2PO4 led to upregulation of proteins including phosphohydrolase, asparagine synthase, and the phosphotransferase system (PTS) transporter subunit EIIC, which related to phosphate metabolism for regulation of uranium mineralization.

Inhibition of Xanthomonas growth by bioactive volatiles from Pseudomonas sp. triggers remarkable changes in the phytopathogen transcriptome

Volatile organic compounds (VOCs) produced by microorganisms may have a noteworthy role in the control of plant pathogens. Xanthomonas are a well-studied group of phytobacteria that cause diverse diseases in economically important crops worldwide. Key species that infect sugarcane are X. albilineans (Xab) and X. axonopodis pv. vasculorum (Xav). Here, we investigated VOC-producing bacteria with antagonistic effects against Xab and Xav. We demonstrated that VOCs produced by Pseudomonas sp. V5-S-D11 was able to abolish the growth of these pathogens. A set of 32 VOCs was identified in the volatilome of V5-S-D11, with 10 showing a concentration-dependent inhibitory effect on both phytobacteria. Among them, dimethyl disulfide (DMDS), a volatile sulfur compound, has the potential to be biotechnologically explored in agriculture since it can improve plant growth and induce systemic resistance against plant pathogens. Interestingly, transcriptomic analysis of Xab treated with DMDS revealed several up-regulated metabolic pathways such as a two-component system, flagellar assembly, chemotaxis, and a bacterial secretion system. Although the ethanol (ETOH) used as DMDS solvent did not inhibit XXab growth, it triggered a similar up-regulation of some genes, indicating that this phytopathogen can deal with ETOH better than DMDS. Overall, this study explores the wide role of VOCs in the interactions with bacteria. Moreover, our results indicate that VOCs from Pseudomonas sp. may represent a novel biotechnological strategy to counteract diseases caused by Xanthomonas species and can be further exploited for sustainable approaches in agriculture.

Dual RNA-Seq Unveils Candidate Key Virulence Genes of Vibrio harveyi at the Early Stage of Infection in Hybrid Grouper (♀ Epinephelus polyphekadion × ♂ E. fuscoguttatus).

Vibrio harveyi is a major bacterial pathogen that causes disease in aquaculture animals worldwide. Although V. harveyi consistently harbors a range of traditional virulence genes, it remains unclear which specific genes are crucial for virulence at different infection stages. Dual RNA-seq is a cutting-edge RNA sequencing technology that is ideal for investigating the gene expression patterns of pathogens within the host, which is highly effective in identifying key virulence genes. In previous artificial infection experiments, we have identified the liver of hybrid grouper (♀ Epinephelus polyphekadion × ♂ E. fuscoguttatus) as the main target organ for pathogenic V. harveyi GDH11385 during the initial infection phase. To further explore the key virulence factors of V. harveyi at the early stage of infection, the liver of the hybrid grouper infected with strain GDH11385 was analyzed here by dual RNA-seq. The transcriptome data were compared with that of in vitro cultured bacteria. The results showed that 326 and 1140 DEGs (differentially expressed genes) were significantly up- and down-regulated, respectively, at 4 h post-infection (hpi). Further pathway enrichment analyses revealed that these up-regulated DEGs in vivo were mainly enriched in siderophore biosynthesis and transport, type VI secretion system (T6SS), flagellar assembly, glycolysis/gluconeogenesis, and ribosome. Notably, all genes involved in the metabolism and utilization of vibrioferrin (a carboxylate class of siderophore produced by Vibrio), and most of the genes within one of three T6SSs, were significantly up-regulated in vivo. This indicates that siderophore-dependent iron competition and T6SS-mediated delivery of virulence factors are vital for the successful colonization of V. harveyi at the early stage of infection. This study provides more precise clues to reveal the virulence mechanism of V. harveyi during the initial phase of infection.

Polysaccharide breakdown products drive degradation-dispersal cycles of foraging bacteria through changes in metabolism and motility

Most of Earth’s biomass is composed of polysaccharides. During biomass decomposition, polysaccharides are degraded by heterotrophic bacteria as a nutrient and energy source and are thereby partly remineralized into CO2. As polysaccharides are heterogeneously distributed in nature, following the colonization and degradation of a polysaccharide hotspot the cells need to reach new polysaccharide hotspots. Even though many studies indicate that these degradation-dispersal cycles contribute to the carbon flow in marine systems, we know little about how cells alternate between polysaccharide degradation and motility, and which environmental factors trigger this behavioral switch. Here, we studied the growth of the marine bacterium Vibrio cyclitrophicus ZF270 on the abundant marine polysaccharide alginate, both in its soluble polymeric form as well as on its breakdown products. We used microfluidics coupled to time-lapse microscopy to analyze motility and growth of individual cells, and RNA sequencing to study associated changes in gene expression. We found that single cells grow at reduced rate on alginate until they form large groups that cooperatively break down the polymer. Exposing cell groups to digested alginate accelerates cell growth and changes the expression of genes involved in alginate degradation and catabolism, central metabolism, ribosomal biosynthesis, and transport. However, exposure to digested alginate also triggers cells to become motile and disperse from cell groups, proportionally increasing with the group size before the nutrient switch, and this is accompanied by high expression of genes involved in flagellar assembly, chemotaxis, and quorum sensing. The motile cells chemotax toward polymeric but not digested alginate, likely enabling them to find new polysaccharide hotspots. Overall, our findings reveal cellular mechanisms that might also underlie bacterial degradation-dispersal cycles, which influence the remineralization of biomass in marine environments.

Polysaccharide breakdown products drive degradation-dispersal cycles of foraging bacteria through changes in metabolism and motility.

Most of Earth's biomass is composed of polysaccharides. During biomass decomposition, polysaccharides are degraded by heterotrophic bacteria as a nutrient and energy source and are thereby partly remineralized into CO2. As polysaccharides are heterogeneously distributed in nature, following the colonization and degradation of a polysaccharide hotspot the cells need to reach new polysaccharide hotspots. Even though many studies indicate that these degradation-dispersal cycles contribute to the carbon flow in marine systems, we know little about how cells alternate between polysaccharide degradation and motility, and which environmental factors trigger this behavioral switch. Here, we studied the growth of the marine bacterium Vibrio cyclitrophicus ZF270 on the abundant marine polysaccharide alginate, both in its soluble polymeric form as well as on its breakdown products. We used microfluidics coupled to time-lapse microscopy to analyze motility and growth of individual cells, and RNA sequencing to study associated changes in gene expression. We found that single cells grow at reduced rate on alginate until they form large groups that cooperatively break down the polymer. Exposing cell groups to digested alginate accelerates cell growth and changes the expression of genes involved in alginate degradation and catabolism, central metabolism, ribosomal biosynthesis, and transport. However, exposure to digested alginate also triggers cells to become motile and disperse from cell groups, proportionally increasing with the group size before the nutrient switch, and this is accompanied by high expression of genes involved in flagellar assembly, chemotaxis, and quorum sensing. The motile cells chemotax toward polymeric but not digested alginate, likely enabling them to find new polysaccharide hotspots. Overall, our findings reveal cellular mechanisms that might also underlie bacterial degradation-dispersal cycles, which influence the remineralization of biomass in marine environments.

The Intersection of the Oral Microbiome and Salivary Metabolites in Head and Neck Cancer: From Diagnosis to Treatment

Head and neck cancers (HNCs) are the seventh most common cancer worldwide, accounting for 4–5% of all malignancies. Salivary metabolites, which serve as key metabolic intermediates and cell-signalling molecules, are emerging as potential diagnostic biomarkers for HNC. While current research has largely concentrated on these metabolites as biomarkers, a critical gap remains in understanding their fluctuations before and after treatment, as well as their involvement in oral side effects. Recent studies emphasise the role of the oral microbiome and its metabolic activity in cancer progression and treatment efficacy by bacterial metabolites and virulence factors. Oral bacteria, such as P. gingivalis and F. nucleatum, contribute to a pro-inflammatory environment that promotes tumour growth. Additionally, F. nucleatum enhances its virulence through flagellar assembly and iron transport mechanisms, facilitating tumour invasion and survival. Moreover, alterations in the oral microbiome can influence chemotherapy efficacy and toxicity through the microbiota–host irinotecan axis, highlighting the complex interplay between microbial communities and therapeutic outcomes. Salivary metabolite profiles are influenced by factors such as gender, methods, and patient habits like smoking—a major risk factor for HNC. Radiotherapy (RT), a key treatment for HNC, often causes side effects such as xerostomia, oral mucositis, and swallowing difficulties which impact survivors’ quality of life. Intensity-modulated radiotherapy (IMRT) aims to improve treatment outcomes and minimise side effects but can still lead to significant salivary gland dysfunction and associated complications. This review underscores the microbial and host interactions affecting salivary metabolites and their implications for cancer treatment and patient outcomes.

Metagenomic Analysis: Alterations of Soil Microbial Community and Function due to the Disturbance of Collecting Cordyceps sinensis

Soil microorganisms are critical to the occurrence of Cordyceps sinensis (Chinese Cordyceps), a medicinal fungi used in Traditional Chinese Medicine. The over-collection of Chinese Cordyceps has caused vegetation degradation and impacted the sustainable occurrence of Cordyceps. The effects of Chinese Cordyceps collection on soil microorganisms have not been reported. Metagenomic analysis was performed on the soil of collecting and non-collecting areas of production and non-production areas, respectively. C. sinensis collection showed no alteration in alpha-diversity but significantly affected beta-diversity and the community composition of soil microorganisms. In Cordyceps production, Thaumarchaeota and Crenarchaeota were identified as the dominant archaeal phyla. DNA repair, flagellar assembly, propionate metabolism, and sulfur metabolism were affected in archaea, reducing the tolerance of archaea in extreme habitats. Proteobacteria, Actinobacteria, Acidobacteria, Verrucomicrobia, and Nitrospirae were identified as the dominant bacterial phyla. The collection of Chinese Cordyceps enhanced the bacterial biosynthesis of secondary metabolites and suppressed ribosome and carbon metabolism pathways in bacteria. A more complex microbial community relationship network in the Chinese Cordyceps production area was found. The changes in the microbial community structure were closely related to C, N, P and enzyme activities. This study clarified soil microbial community composition and function in the Cordyceps production area and established that collection clearly affects the microbial community function by altering microbial community structure. Therefore, it would be important to balance the relationship between cordyceps production and microbiology.

FAP20 is required for flagellum assembly in Trypanosoma brucei.

Trypanosoma bruceiis a human and animal pathogen that depends on flagellar motility for transmission and infection. The trypanosome flagellum is built around a canonical "9+2" axoneme, containing nine doublet microtubules (DMTs) surrounding two singlet microtubules. Each DMT contains a 13-protofilament A-tubule and a 10-protofilament B-tubule, connected to the A-tubule by a conserved, non-tubulin inner junction (IJ) filament made up of alternating PACRG and FAP20 subunits. Here we investigate FAP20 in procyclic formT. brucei. A FAP20-NeonGreen fusion protein localized to the axoneme as expected. Surprisingly, FAP20 knockdown led to a catastrophic failure in flagellum assembly and concomitant lethality. This differs from other organisms, where FAP20 is required for normal flagellum motility, but generally dispensable for flagellum assembly and viability. Transmission electron microscopy demonstrates failed flagellum assembly in FAP20 mutants is associated with a range of DMT defects and defective assembly of the paraflagellar rod, a lineage-specific flagellum filament that attaches to DMT 4-7 in trypanosomes. Our studies reveal a lineage-specific requirement for FAP20 in trypanosomes, offering insight into adaptations for flagellum stability and motility in these parasites and highlighting pathogen versus host differences that might be considered for therapeutic intervention in trypanosome diseases.

Screening and functional characterization of isocitrate lyase AceA in the biofilm formation of Vibrio alginolyticus.

Biofilm is a well-known sessile lifestyle for bacterial pathogens, but a little is known about the mechanism on biofilm formation in Vibrio alginolyticus. In this study, we screened V. alginolyticus strains with strong biofilm formation ability from coastal seawater. The antibiotic resistance of the biofilm cells (BFs) was higher than that of the planktonic cells (PTs). To study the genes and pathways involved in biofilm formation, we performed transcriptome analysis of the BFs and PTs of V. alginolyticus R9. A total of 685 differentially expressed genes (DEGs) were upregulated, and 517 DEGs were downregulated in the BFs. The upregulated DEGs were significantly enriched in several pathways including glyoxylate and dicarboxylate metabolism, while the downregulated genes were significantly enriched in the flagellar assembly pathways. The key gene involved in glyoxylate shunt, aceA, was cloned, and ΔaceA mutant was constructed to determine the function of AceA in carbon source utilization, biofilm formation, and virulence. Real-time reverse transcription PCR showed that the expression of aceA was higher at the mature stage but lower at the disperse stage of biofilm formation, and the expression of the flagellar related genes was upregulated in ΔaceA. This is the first study to illustrate the global gene expression profile during the biofilm formation of V. alginolyticus, and isocitrate lyase AceA, the key enzyme involved in glyoxylate shunt, was shown to maintain biofilms accompanied by downregulation of flagellation but promoted dispersal of BFs at the late stage.IMPORTANCEBiofilms pose serious public problems, not only protecting the cells in it from environmental hazard but also affecting the composition and abundance of bacteria, algae, fungi, and protozoa. The important opportunistic pathogen Vibrio alginolyticus is extremely ubiquitously present in seawater, and it also exhibited a strong ability to form biofilm; thus, investigation on the biofilm formation of V. alginolyticus at molecular level is fundamental for the deeper exploration of the environmental concerns arose by biofilm. In this study, transcriptome analysis of biofilm cells (BFs) and planktonic cells (PTs) from V. alginolyticus was performed and AceA was screened to play an important role in biofilm formation. AceA was shown to maintain biofilms accompanied by downregulation of flagellation but promoted dispersal of BFs at the disperse stage. This method was helpful to further understand the ability and mechanism of V. alginolyticus biofilm formation and provide clues for prevention of V. alginolyticus infection.

Effect of body mass index on semen quality, sperm chromatin integrity and sperm DNA methylation

Obesity represents a growing problem due to its impacts on human health and reproduction. In this study, we analysed semen quality, sperm DNA integrity and gene-specific CpG methylation in 116 healthy men from normal population. The men were divided into three groups according to their body mass index (BMI), and their ejaculates were analysed using standard methods, sperm chromatin structure assay (SCSA), methylation next generation sequencing (NGS) and amplicon sequencing. The sperm methylation NGS revealed six significantly differentially methylated regions (DMRs). Using subsequent targeted amplicon sequencing in 116 men, two of the DMRs were proved as differentially methylated in sperm of men with normal BMI vs. BMI ≥ 25. The DMRs were located in the EPHA8 and ANKRD11 gene. Also, we detected a significant decline in the EPHA8, ANKRD11 and CFAP46 gene methylation in association with increasing BMI values. The genes EPHA8 and ANKRD11 are involved in the nervous system and brain development; the CFAP46 gene plays a role in a flagellar assembly and is associated with sperm motility. Significantly lower rates of motile and progressive motile sperm were observed in men with BMI ≥ 30. Our results show that excess body weight can modify CpG methylation of specific genes, affect sperm motility, and compromise sperm chromatin integrity. These factors can stand behind the observed reduced fertility in men with obesity. The methylation changes might be transmitted to their offspring through sperm, and become a basis for possible developmental and reproductive issues in the next generation.

WDR64, a testis-specific protein, is involved in the manchette and flagellum formation by interacting with ODF1

The WD40 repeat (WDR) domain is present in a wide range of proteins, providing sites for protein‒protein interactions. Recent studies have shown that WDR proteins play indispensable roles in spermatogenesis, such as in spermatocyte division, sperm head formation and flagellar assembly. In this study, we identified a novel testis-specific gene, WDR64, which has the typical characteristics of WD40 proteins with two β-propellers, and is highly conserved in Mammalia. RT-PCR and Western blot results revealed that WDR64 was highly expressed in testis. WDR64 protein was weakly expressed at postnatal Day 7, increased substantially at postnatal Day 28 and maintained at high levels thereafter. Further immunofluorescence demonstrated that WDR64 was localized posterior to the nucleus in steps 8–14 spermatids in line with the dynamic localization of manchette, moved to the flagella in steps 15–16 spermatids, and localized at the midpiece of the flagellum in mature spermatozoa. To explore the function of WDR64, we performed immunoprecipitation‒mass spectrometry (IP‒MS) to screen its interacting proteins and found that WDR64 interacted with ODF1 to form a complex. The WDR64/ODF1 complex is located at the manchette during nucleus shaping and finally at the midpiece of the mature spermatozoa tail, suggesting that it may be involved in the assembly of the manchette and flagella during spermiogenesis. Our findings provide the first understanding of the expression pattern of WDR64 and its potential molecular mechanism in spermiogenesis.

Lignin-derived compounds assisted with Kocuria marina H-2 and Pseudomonas putida B6-2 co-culture enhanced naphthalene biodegradation

The implementation of environmentally friendly and sustainable remediation strategies positively impacts solid waste management. In this study, the Kocuria marina H-2 and Pseudomonas putida B6-2 co-culture system demonstrated enhanced naphthalene biodegradation efficiency compared to single-strain cultures. Under optimal conditions of 35 °C, 200 rpm/min, and a 1:1 ratio of the co-culture system, the naphthalene biodegradation potential was further increased. Notably, the addition of both ethylenediamine-pretreated lignin and p-hydroxybenzoic acid significantly elevated naphthalene degradation rates to 68.5 %. In addition, the oil-liquid surface tension decreased, while cell surface hydrophobicity and colony-forming units increased with the addition of lignin-derived compounds. The modification of naphthalene bioavailability by ethylenediamine-pretreated lignin would accelerate the uptake and transport of hydrocarbons via ABC transporters and flagellar assembly. Importantly, genes related to bacterial chemotaxis and fatty acid biosynthesis were upregulated during the co-metabolism of naphthalene and p-hydroxybenzoic acid, further enhancing naphthalene bioconversion.

Chirality differences of three borneols contribute to controlling Escherichia coli biofilm formation by chemotaxis mediating movement

SummaryEscherichia coli (E. coli) biofilm is the major cause of its high lethality in foodborne illness. Controlling E. coli biofilm formation is a critical way to reduce foodborne diseases. Here, chiral borneol isomers (L‐borneol, D‐borneol, and isoborneol) were identified as E. coli chemorepellents, which reduced reversible adhesion at the initial stage of biofilm formation. Borneols directly inhibited biofilm production and their inhibitory capacities were associated with the chiral stereochemical structures (L‐borneol > D‐borneol > isoborneol). A transcriptomic study revealed the inhibitory mechanism of borneols was attributed to the bacterial motility intention and motility energy system. The most effective isomer, L‐borneol, reduced bacterial energy metabolism and increased E. coli chemotaxis motility intention through the up‐regulation of genes associated with flagellar assembly and bacterial chemotaxis pathways. This work demonstrates that borneols are biofilm inhibitors and supports the potential of borneols as a stereochemical antimicrobial strategy to reduce foodborne pathogenic bacterial contamination.

Novel insights into biofilm formation and the key differentially expressed genes in Yersinia enterocolitica from meat: Implications for food safety and disease prevention

Yersinia enterocolitica is an important foodborne pathogen that can cause a zoonotic disease known as yersiniosis, which causes symptoms such as acute diarrhea, mesenteric adenitis, terminal ileum inflammation, pseudo appendicitis, sepsis, and other complications. The mechanism of biofilm formation in Y. enterocolitica remains poorly understood, with limited research available on this topic. This study systematically examined the distribution characteristics and biofilm formation ability of Y. enterocolitica isolated from poultry and livestock related samples. Analysis of food samples collected indicated significant presence of Y. enterocolitica (207/670, 30.9 %), particularly in frozen duck meat (7/11, 63.6 %). Majority of the isolated strains did not demonstrate biofilm-forming ability (52.7 %), while a notable percentage exhibited moderate (6.8 %) to strong (11.6 %) biofilm-forming ability. Additionally, a significant percentage of strains (16/207, 7.7 %) displayed extremely high optical density/cut-off OD (OD/ODC) ratios (the average OD value of each sample divided by the average OD value of the negative controls of each 96-well plate plus 3 standard deviations) (exceeding 10). Time-course analysis of biofilm formation in 10 isolates revealed three distinct patterns: (i) rapid increase from 6 h to 12 h, with gradual peak between 48 and 72 h followed by a slight decline and stabilization; (ii) little biofilm formation at 24 h with a gradual increase up to 96 h, maintaining this level until 120 h; and (iii) complete absence of biofilm formation throughout the experiment. Subsequent examination of differentially expressed genes (DEGs) in planktonic cells and biofilms of two strains with distinct biofilm formation capabilities identified seven metabolic pathways, including ribosome, photosynthesis, fatty acid degradation, valine, leucine, and isoleucine degradation, as well as pinene, camphor, and geraniol degradation. Significantly elevated expression levels of genes associated with flagellar assembly, bacterial chemotaxis, and quorum sensing (partially) were observed exclusively in planktonic cells of the selected strain with stronger biofilm-forming ability, implying that the heightened expression of flagellar assembly and bacterial chemotaxis-related genes is an important but not sole determinant of biofilm formation. The study contributes to the elucidation of the underlying mechanisms governing biofilm formation in Y. enterocolitica and may offer valuable insights for the advancement of novel food safety strategies.

Transcriptomics analysis of the role of SdiA in desiccation tolerance of Cronobacter sakazakii in powdered infant formula

The quorum-sensing receptor SdiA is vital for regulating the desiccation tolerance of C. sakazakii, yet the specific mechanism remains elusive. Herein, transcriptomics and phenotypic analysis were employed to explore the response of C. sakazakii wild type (WT) and sdiA knockout strain (ΔsdiA) under drying conditions. Following 20 days of drying in powdered infant formula (PIF), WT exhibited 4 log CFU/g higher survival rates compared to ΔsdiA. Transcriptome revealed similar expression patterns between csrA and sdiA, their interaction was confirmed both by protein-protein interaction analysis and yeast two-hybrid assays. Notably, genes associated with flagellar assembly and chemotaxis (flg, fli, che, mot regulon) showed significantly higher expression levels in WT than in ΔsdiA, indicating a reduced capacity for flagellar synthesis in ΔsdiA, which was consistent with cellular morphology observations. Similarly, genes involved in trehalose biosynthesis (ostAB, treYZS) and uptake (thuEFGK) exhibited similar expression patterns to sdiA, with higher levels of trehalose accumulation observed in WT under desiccation conditions compared to ΔsdiA. Furthermore, WT demonstrated enhanced protein and DNA synthesis capabilities under desiccation stress. Higher expression levels of genes related to oxidative phosphorylation were also noted in WT, ensuring efficient cellular ATP synthesis. This study offers valuable insights into how SdiA influences the desiccation tolerance of C. sakazakii, paving the way for targeted strategies to inhibit and control this bacterium.

Association of novel DNAH11 variants with asthenoteratozoospermia lead to male infertility

BackgroundBi-allelic variants in DNAH11 have been identified as causative factors in Primary Ciliary Dyskinesia, leading to abnormal respiratory cilia. Nonetheless, the specific impact of these variants on human sperm flagellar and their involvement in male infertility remain largely unknown.MethodsA collaborative effort involving two Chinese reproductive centers conducted a study with 975 unrelated infertile men. Whole-exome sequencing was employed for variant screening, and Sanger sequencing confirmed the identified variants. Morphological and ultrastructural analyses of sperm were conducted using Scanning Electron Microscopy and Transmission Electron Microscopy. Western Blot Analysis and Immunofluorescence Analysis were utilized to assess protein levels and localization. ICSI was performed to evaluate its efficacy in achieving favorable pregnancy outcomes for individuals with DNAH11 variants.ResultsIn this study, we identified seven novel variants in the DNAH11 gene in four asthenoteratozoospermia subjects. These variants led the absence of DNAH11 proteins and ultrastructure defects in sperm flagella, particularly affecting the outer dynein arms (ODAs) and adjacent structures. The levels of ODA protein DNAI2 and axoneme related proteins were down regulated, instead of inner dynein arms (IDA) proteins DNAH1 and DNAH6. Two out of four individuals with DNAH11 variants achieved clinical pregnancies through ICSI. The findings confirm the association between male infertility and bi-allelic deleterious variants in DNAH11, resulting in the aberrant assembly of sperm flagella and contributing to asthenoteratozoospermia. Importantly, ICSI emerges as an effective intervention for overcoming reproductive challenges caused by DNAH11 gene variants.

Carbon chain elongation characterizations of electrode-biofilm microbes in electro-fermentation

The higher efficiency of electro-fermentation in synthesizing medium-chain fatty acids (MCFAs) compared to traditional fermentation has been acknowledged. However, the functional mechanisms of electrode-biofilm enhancing MCFAs synthesis remain research gaps. To address this, this study proposed a continuous flow electrode-biofilm reactor for chain elongation (CE). After 225 days of operation, stable electrode-biofilms formed and notably improved caproate yield by more than 38 %. The electrode-biofilm was enriched with more CE microorganisms and electroactive bacteria compared to the suspended sludge microorganisms, including Caproicibacterium, Oscillibacter and Pseudoramibacter. Besides, the upregulated CE pathways were evaluated by metagenomic analysis, and the results indicated that the pathways such as acetyl-CoA and malonyl-[acp] formation, reverse beta-oxidation, and fatty acid biosynthesis pathway were all markedly enhanced in cathodic biofilm, more than anodic biofilm and suspended microorganisms. Moreover, microbial community regulated processes like bacterial chemotaxis, flagellar assembly and quorum sensing, crucial for electrode-biofilm formation. Electron transfer, energy metabolism, and microbial interactions were found to be prominently upregulated in the cathodic biofilm, surpassing levels observed in anodic biofilm and suspended sludge microorganisms, which further enhanced CE efficiency. In addition, the statistical analyses further highlighted key microbial functions and interactions within the cathodic biofilm. Oscillospiraceae_bacterium was identified to be the most active microbe, alongside pivotal roles played by Caproiciproducens_sp._NJN-50, Clostridiales_bacterium, Prevotella_sp. and Pseudoclavibacter_caeni. Eventually, the proposed microbial collaboration mechanisms of cathodic biofilm were ascertained. Overall, this study uncovered the biological effects of the electrode-biofilm on MCFAs electrosynthesis, thereby advancing biochemicals production and filling the knowledge gaps in CE electroactive biofilm reactors.

RpoS sigma factor mediates adaptation and virulence in Vibrio mimicus

The alternative sigma factor RpoS functions as a regulator of stress and virulence response in numerous bacterial species. Vibrio mimicus is a critical opportunistic pathogen causing huge losses to aquaculture. However, the exact role of RpoS in V. mimicus remains unclear. In this study, rpoS deletion mutant of V. mimicus was constructed through allelic exchange and the phenotypic and transcriptional changes were investigated to determine the function of RpoS. The abilities of growth, motility, biofilm production, hemolytic activity and pathogenicity were significantly impaired in ΔrpoS strain. Stationary-phase cells of ΔrpoS strain showed lower tolerance to H2O2, heat, ethanol, and starvation stress than the wild-type strain. Transcriptome analyses revealed the involvement of rpoS in various cellular processes, notably bacterial-type flagellum synthesis and assembly, membrane synthesis and assembly and response to various stimuli. Phenotypic and RNA-seq analysis revealed that RpoS is required for biofilm formation, stress resistance, and pathogenicity in V. mimicus. Furthermore, β-galactosidase activity showed that rpoS is essential for optimal transcription of the flgK, fliA, cheA, mcpH mRNA. These results offer significant insight into the function and regulatory network of rpoS/RpoS, thereby improving our understanding and facilitating selection of molecular targets for future prevention strategies against V. mimicus.

VirB11, a traffic ATPase, mediated flagella assembly and type IV pilus morphogenesis to control the motility and virulence of Xanthomonas albilineans.

Xanthomonas albilineans (Xal) is a gram-negative bacterial pathogen responsible for developing sugarcane leaf scald disease, which engenders significant economic losses within the sugarcane industry. In the current study, homologous recombination exchange was carried out to induce mutations within the virB/D4-like type IV secretion system (T4SS) genes of Xal. The results revealed that the virB11-deletion mutant (ΔvirB11) exhibited a loss in swimming and twitching motility. Application of transmission electron microscopy analysis further demonstrated that the ΔvirB11 failed to develop flagella formation and type IV pilus morphology and exhibited reduced swarming behaviour and virulence. However, these alterations had no discernible impact on bacterial growth. Comparative transcriptome analysis between the wild-type Xal JG43 and the deletion-mutant ΔvirB11 revealed 123 differentially expressed genes (DEGs), of which 28 and 10 DEGs were notably associated with flagellar assembly and chemotaxis, respectively. In light of these findings, we postulate that virB11 plays an indispensable role in regulating the processes related to motility and chemotaxis in Xal.