Current Microbiology最新文献

Plant Growth-Promoting Rhizobacteria (PGPR) are gaining increasing attention, but their interactions with indigenous rhizosphere microbiomes remain unclear. To address this issue, we isolated a strain of Priestia aryabhattai with a growth-promoting effect. Under greenhouse conditions, its growth-promoting effect on alfalfa was evaluated, and amplicon sequencing was used to analyze changes in the rhizosphere microbial community to explore the growth promotion mechanism. Our study shows that inoculation with Priestia aryabhattai increases the α-diversity index of the alfalfa rhizosphere microbiome and enhances the abundance of beneficial bacterial genera. This is likely because inoculation with Priestia aryabhattai increased the abundance of carbon-sequestering genera, particularly Gemmatimonas, thereby improving the soil environment. The increased abundance of beneficial bacteria stimulates root development in alfalfa and enhances nutrient uptake, particularly phosphorus, which in turn boosts photosynthesis and promotes alfalfa growth. In summary, Priestia aryabhattai improves soil environment and promotes alfalfa growth by enhancing the carbon sequestration capacity of the rhizosphere microbial community. This work provides theoretical support and insight for the development of PGPR inoculants and for further research on their mechanisms.

In recent years, agar-degrading bacteria have gained significant interest due to their biotechnological, environmental, microbiological, and industrial applications. Agar poses challenges such as marine waste accumulation, difficult industrial processing, limited natural degradability, and sustainability concerns due to high demand and overharvesting of red algae. The present study addresses the need for efficient agar-degrading microorganisms by isolating Aliagarivorans sp. strain DM1 from biofilm on fabric surfaces in the intertidal regions of the Arabian Sea, India. Phylogenetic analysis revealed that strain DM1 is closely related to Aliagarivorans taiwanensis AAT1^T, and it exhibited significant agar-degrading activity on Zobell marine agar plates. Whole genome sequencing of Aliagarivorans sp. strain DM1, conducted using the Illumina NovaSeq platform, yielded a genome size of 4,898,415 bp with an average G + C content of 53.3%. The genome includes 4,518 predicted protein-coding genes (CDS), 86 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes, with thirteen predicted agarases identified. The highest enzyme activity recorded was 51.00 U mL^-1 on the 6th day of incubation using 10% inoculum, with optimal conditions of pH 8-9, 0.8 M NaCl, and temperatures between 50 and 60 °C. These findings underscore the promise of Aliagarivorans sp. strain DM1 in developing efficient enzymatic processes that can be applied in various biotechnological and industrial fields, including waste management and agaro-oligosaccharide production. Furthermore, strain DM1 possesses several key characteristics that enhance its adaptability and utility in marine and industrial applications, surpassing closely related strains in enzyme stability, environmental tolerance, and industrial versatility.

The disposal of electronic waste (EW) in open landfills has caused several toxic environmental effects. The harmful metallic components released in the environment due to deposition of EW act as hazards for living systems. EW management has been widely studied in recent days across the world. Though, several processes are implemented in extraction, recycling and recovery of heavy metals from the EW, most of them are not effective in recovering the precious metals. Various chemical processes are executed for efficient extraction of precious metals from e-wastes. Though the techniques are easy to process and rapid, however, the chemical leaching also has detrimental environmental consequences. Biological approaches, on the other hand, solves the purpose for efficient and environmentally friendly recovery of precious metals. Thus, both resource recovery as well as remediation can be targeted simultaneously. Biotechnological methods offer sustainable and efficient solutions for metal recovery from electronic wastes, presenting a viable alternative to traditional methods. Continued advancements in this field hold significant promise for addressing the growing e-waste challenge.

Rhizobial exopolysaccharides (EPS) may provide stabilization of membranes against external factors, as well as improved surface adhesion, but their role in interaction with legume and non-legume plants is still far from understanding. In this work, the transcriptional regulator RosR of Rhizobium ruizarguesonis, which regulates the synthesis of EPS, was overproduced in a pHC60 plasmid and expressed in the RCAM 1026 strain. This resulted in an improved production of EPS by this recombinant strain. Comparative analysis of the inoculation of pea Pisum sativum plants with R. ruizarguesonis pHC60-rosR and strain carrying the empty plasmid revealed an essential increase in the number of nodules, root length and biomass in plants inoculated with this EPS-overproducing strain. It demonstrates that the enhanced EPS synthesis by rhizobia may stimulate plant root colonization and subsequent nodule formation in pea plants. The influence of enhanced EPS synthesis in rhizobia on colonizing activity was also estimated in non-legume plant tomato Solanum lycopersicum. Our findings shown the increased colonization of the root surface and stimulation of the shoot biomass of inoculated plants. Inoculation of pea and tomato with EPS-overproducing rhizobial strain essentially increased plant resistance to phytopathogenic fungi Fusarium culmorum and F. oxysporum in both legume and non-legume plants, demonstrating a significant biocontrol effect of this recombinant strain. Furthermore, we have identified the PsLYK10 gene that encodes a putative EPS receptor in P. sativum, although no significant effect of PsLYK10 overexpression on nodulation in legume (pea P. sativum) and colonization of roots of non-legume plants by rhizobia was found compared to enhanced production of EPS by rhizobia.

ZIKV was a mosquito-borne neglected tropical pathogen until it spread into the Pacific and South America, followed by large human outbreaks related to congenital abnormalities in neonates and neurological disorders in adults. The following study used the C57BL/6 IFNAR1 receptor knockout (IFN AR1^-/-) mouse model to understand the role of selected cytokines and apoptotic factors in the pathogenicity of ZIKV strain PRVABC59. Mice infected with 10² particles of Zika viruses died until 9 days post infection. The brain, spleen, and lung were collected from intramuscularly infected mice on day 6 post infection (pi) to quantify the mRNA expression of targeted cytokines and apoptosis-mediated factors by RT-qPCR. Upregulation of IL-6, IL-17α, IFN-α, and IFN-β were found in the brain and lung of infected mice. IFN-γ was also significantly upregulated in the infected brain and spleen. The collective findings from our study indicate that a strong immune response was developed against ZIKV PRVABC59 in the infected mice brain.

Still, it remains a debate after four decades of research on surviving cells, several bacterial species were naturally inducted and found to exist in a viable but non-culturable (VBNC) state, an adaptive strategy executed by most bacterial species under different stressful conditions. VBNC state are generally attributed when the cells lose its culturability on standard culture media, diminish in conventional detection methods, but retaining its viability, virulence and antibiotic resistance over a period of years and may poses a risk to marine animals as well as public health and food safety. In this present review, we mainly focus the VBNC state of Vibrios and other human bacterial pathogens. Exposure to several factors like nutrient depletion, temperature fluctuation, changes in salinity and oxidative stress, antibiotic and other chemical stress can induce the cells to VBNC state. The transcriptomic and proteomic changes during VBNC, modification in detection techniques and the most significant role of Rpf in conversion of VBNC into culturable cells. Altogether, detection of unculturable VBNC forms has significant importance, since it may not only regain its culturability, but also reactivate its putative virulence determinants causing serious outbreaks and illness to the individual.

Acinetobacter baumannii and Acinetobacter nosocomialis are the imperious pathogens in the intensive care units. We aimed to explore the genomic features of these pathogens to understand the factors influencing their plasticity. Using next-generation sequencing, two carbapenem-resistant A. baumannii (AbaBS-3, AbaETR-4) isolates and a pan-susceptible A. nosocomialis (AbaAS-5) isolate were characterised. All genomes exhibited 94% similarity with a degree of heterogeneity. AbaBS-3 and AbaETR-4 harboured antibiotic resistance gene (ARG) repertoire to most antibiotic classes. Carbapenem resistance was due to blaOXA-23 and blaOXA-66 besides the antibiotic efflux pumps. Diverse mobile genetic elements (MGE), insertion sequences (IS), prophages and virulence determinants with a plethora of stress response genes were identified in all three genomes. Class-1 integron in AbaETR-4, encoded genes that confer resistance to aminoglycosides, phenicol, sulfonamides and disinfectants. Substitutions in LpxACD and PmrCAB of AbaETR-4 confirmed the colistin resistance in vitro. Novel mutations in piuA, responsible for transporting cefiderocol, were found in AbaBS-3 and AbaETR-4. Plasmids carrying toxin-antitoxin systems, ARGs and ISs were present in these genomes. All three genomes harboured diverse protein secretion systems, virulence determinants related to immune evasion, adherence, biofilm formation and iron acquisition systems. AbaAS-5 exclusively harboured serine protease pkf, and CpaA substrate of type-II secretion system but lacked the acinetobactin-iron acquisition system. Our work delivers a holistic genome characterization of A. baumannii, coupled with a trailblazing attempt to study A. nosocomialis from India. The presence of ARGs and potential virulence factors interspersed with MGE is a cause for concern, depicting the dynamic adaptability mediated by genetic recombination.

A Gram-stain-negative, aerobic, mesophilic, motile, rod-shaped bacterium, designated strain TUF1^T, was isolated from a karst wetland in south-west China. It was demonstrated to be capable of growing on plates containing oxytetracycline, streptomycin, or ofloxacin as the sole carbon source. Phylogenetic analysis of the 16S rRNA gene sequence revealed that this organism belongs to the genus Sphingopyxis and is closely related to S. chilensis S37^T (99.17%) and S. alaskensis RB2256^T (99.12%). The orthologous average nucleotide identity values (OrthoANIu, 84.42% and 87.53%) and digital DNA-DNA hybridization values (dDDH, 41.7% and 48.9%) between strain TUF1^T and its close relatives were all below the standard recommended threshold values for species discrimination. The genomic DNA G + C content was determined to be 64.7%. The predominant cellular fatty acids were identified as summed feature 8 (C_18:1ω7c and/or C_18:1ω6c) and summed feature 3 (C_16:1ω7c and/or C_16:1ω6c). The major polar lipids found to be diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, and sphingoglycolipid. The sole respiratory quinone present was ubiquinone Q10. Based on the phylogenetic, biochemical, physiological, and chemotaxonomic analyses, strain TUF1^T represents a novel species of the genus Sphingopyxis. The designation "Sphingopyxis kveilinensis sp. nov." is proposed as the name for this novel species, and the strain TUF1^T (= CGMCC1.62043 ^T = JCM36394^T) is designated as the type strain.

Avocado cultivation holds significant economic importance in many countries, ranking Colombia as the fifth largest global producer. Particularly, the Hass cultivar plays a pivotal role in Colombia's avocado industry, especially in the Department of Antioquia, the primary export region. This cultivar is grown under diverse soil and climate conditions and exhibits considerable genetic polymorphism due to the hybridization of varieties of agronomic significance, leading to a diverse array of landrace rootstocks. However, the role of soil conditions and rootstock genotype in structuring rhizosphere bacterial communities is still lacking. In addressing this knowledge gap, we investigated the influence of two soil conditions on the structure of rhizosphere bacterial communities associated with two landrace genotypes of Persea americana cv. Hass, utilizing 16S rRNA sequencing. Notably, no significant differences related to genotypes were observed. This study reports that the rhizosphere bacterial microbiome remains consistent across avocado landrace rootstocks, while variations in key parameters such as phosphorus, pH, Mg, and Ca drive distinct rhizosphere effects. Our results reveal that despite the soils having similar management, increases in these crucial parameters can lead to bacterial communities with lower alpha diversity and a more complex co-occurrence network. In addition, we found substantial variations in beta diversity, bacterial composition, and metagenome predictions between the two farms, underscoring the role of soil variables in shaping the bacterial microbiome. These findings provide valuable insights into the factors influencing the bacterial communities that may play a role in the health and productivity of crops with agro-industrial potential, such as Hass avocado.

Lead (Pb) is a hazardous environmental pollutant that threatens soil health, water quality, and agricultural productivity. Plant growth-promoting rhizobacteria (PGPRs) mediated bioremediation is considered as an eco-friendly approach for agro-environmental sustainability. This study investigated the Pb bioremediation potential of Bacillus altitudinis (IHBT-705). The results revealed that IHBT-705 strain tolerated upto 15 mM of Pb, possessed 96% Pb bioaccumulation efficiency, and also maintained its plant growth-promoting (PGP) traits under Pb stress. Furthermore, IHBT-705 strain treated with 15 mM Pb solution (IHBT-W) and soil containing 15 mM Pb treated with IHBT-705 inoculum (IHBT-S) ameliorated the detrimental effects of Pb stress. Both IHBT-W and IHBT-S treatment significantly improved the shoot length, root length, total roots, chlorophyll content, and antioxidants enzyme activity of the rice seedlings as compared to the seedlings treated with 15 mM Pb solution (Pb-W) and soil containing 15 mM Pb (Pb-S). Also, IHBT-W and IHBT-S treatment decreased the Pb content in the rice plant by 97 and 96% over their respective Pb-W and Pb-S plants. Overall, our research underscores the remarkable Pb bioremediation potential of IHBT-705, offering a promising avenue for dual function, i.e. improving soil health and promoting plant growth under Pb contamination.