International Microbiology最新文献

Strain HM32M-2 ^T, an aerobic, catalase-positive, oxidase-positive, and Gram-stain-negative bacterium, was isolated from a sandy sediment sample collected from Qinzhou Gulf in Guangxi Zhuang Autonomous Region, China. Strain HM32M-2 ^T grew at 15-37 °C (optimum, 30 °C), at pH 5.5-9.5 (optimum, pH 8.5), and with 1.0-12.0% (w/v) NaCl (optimum, 3.0%). Strain HM32M-2 ^T exhibited the highest 16S rRNA gene sequence similarity with Sedimentitalea nanhaiensis NH52F^T (98.4%). Phylogenetic analyses based on 16S rRNA gene sequences and whole-genome sequences showed that strain HM32M-2 ^T formed a distinct lineage with Sedimentitalea nanhaiensis NH52F^T. The draft genome of strain HM32M-2 ^T was 3.40 Mbp in size and its DNA G + C content was 63.6%. Comparative genome analysis revealed that average nucleotide identity and digital DNA-DNA hybridization among strain HM32M-2 ^T and other Sedimentitalea species were below cut-off levels of 95-96% and 70%, respectively. Chemotaxonomic analyses indicated that strain HM32M-2 ^T contained Q-10 as the respiratory quinone, C_18:1ω7c as the major cellular fatty acid, and diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, one unidentified aminolipid, and one unidentified lipid as the major polar lipids. Strain HM32M-2 ^T had a typical chemical composition of fatty acids, polar lipids, and quinones for Sedimentitalea species, but could be distinguished from known species of the genus Sedimentitalea. On the basis of the polyphasic evidence, strain HM32M-2 ^T should be classified as a novel species of the genus Sedimentitalea, for which the name Sedimentitalea sediminis sp. nov. is proposed. The type strain is HM32M-2 ^T (= MCCC 1K08873^T = KCTC 8272 ^T).

This study aimed to develop a selenium nanoparticles (SeNPs)-enriched probiotic strain with potential anti-hangover effects. Pediococcus acidilactici JW-015 was screened for its high tolerance to inorganic selenium (up to 80 mM sodium selenite) and efficient synthesis of SeNPs, achieving a selenium accumulation concentration of 6974 ± 90.71 μg/g, with SeNPs accounting for 86.54% ± 2.48%. Safety and probiotic properties were evaluated, confirming that JW-015 is a safe probiotic strain and that selenium enrichment enhanced its probiotic properties. Furthermore, JW-015 demonstrated significant anti-hangover efficacy, with selenium enrichment improving the oxidative stress capacity, alcohol tolerance, alcohol degradation ability, and relevant enzyme activities (ADH and ALDH) of the strain. This study provides a promising bio-carrier for SeNPs transformation and expands the applications of selenium-enriched LAB.

Mobilization and release of arsenic (As) from the soil matrix is essential to promote the in situ remediation efficiency of As-contaminated soil. In the current study, two aerobic As(V)-reducing strains Leclercia sp. SMR8 and Klebsiella sp. SMR14 were isolated from As-contaminated soils. The As(V) reduction capacity was mediated by the arsC gene which was successfully amplified from both strains. The bacterial growth characteristics were evaluated, and both strains demonstrated good environmental adaptability with high As(V) tolerance, wide growth temperature range, and utilization of various carbon substrates. Except for bacterial growth and regulation of ars genes, initial As(V) concentration was confirmed as the dominant factor impacting the As(V) reduction rate by the strains. The reduced As(V) proportion decreased from 95 to 70% with increasing the initial As(V) concentration from 100 to 600 mg/L. The results of soil extraction experiments showed that the addition of the strains promoted As extraction efficiency from contaminated soil, and the process was significantly influenced by the added carbon substrates. SMR14 using glucose as a carbon source exhibited excellent extraction efficiency, indicating application potential in soil remediation.

Tylenchulus semipenetrans is a soil-borne pathogen that causes substantial damage and economic losses to citrus crops worldwide. Due to the high toxicity of chemical nematicides to humans and the environment, biocontrol bacteria have emerged as a promising alternative for managing citrus nematodes. This study aimed to screen bacterial strains for their efficacy to control T. semipenetrans and assess their impact on citrus plant growth. A total of 107 bacterial strains were isolated from the soil and roots of infested citrus trees. Among these, five strains exhibited significant nematicidal activity against T. semipenetrans. Four bacterial densities were tested for each strain: 3.6 × 10⁵, 2.5 × 10⁴, 3.6 × 10³, and 1.2 × 10³ cells/ml. These strains were tested both individually and in combination to evaluate their efficacy. The five strains were identified as Variovorax paradoxus, Bacillus pseudomycoides, Bacillus simplex, Bacillus cereus, and Paracoccus speluncae based on physiological, biochemical, and molecular (16S rRNA gene sequences) analyses. Juvenile mortality (J2s) and egg hatching inhibition were positively correlated with bacterial concentration and exposure duration. The highest juvenile mortality (100%) was observed with a combination of all five bacteria (3.6 × 10⁵ cells/ml) after 96 h, while B. cereus alone achieved 98.98% mortality. The maximum nematicidal activities of the bacterial filtrates were generally observed between the 4th and 6th days of incubation, coinciding with peak bacterial growth and biomass production. The selected isolates also demonstrated the ability to produce indole acetic acid and solubilize phosphorus. In greenhouse experiments, the five isolates reduced T. semipenetrans populations by up to 62.96% compared to the control. Additionally, all rhizosphere bacteria and their combination significantly enhanced plant growth parameters (p < 0.0001). Notably, P. speluncae BR21 has not previously been tested for nematicidal effects on any nematode, making this the first documented report of its nematicidal potential.

The halotolerant obligate methanotroph Methylotuvimicrobium alcaliphilum 20Z is a promising biotechnological strain that has been repeatedly tested as a producer of high-added-value polycarbon compounds. The mutant M. alcaliphilum 20Z-3E lacking two fumarases and a malic enzyme is a potential fumarate producer. The analysis of strand-specific 3'-end sequencing of mRNA did not reveal any effects of the mutations on the central metabolism of the methanotroph; however, it showed a dramatic change in the expression of putative iron transport genes, as well as some genes associated with stress response. When the strain 20Z-3E grows at low salinity under methane, some part of fumarate is formed from aspartate, since the increase in salinity results in the biosynthesis of ectoine and the decrease in fumarate concentration. However, when the strain grows on methanol, the fumarate pool is lower and does not depend on the salinity of the medium. Our results have shown that deletion of the mae gene encoding malic enzyme makes a significant contribution to the fumarate accumulation. The strain 20Z-2F with the deletion of only two genes, fumI and fumII, demonstrated delayed growth under methane in comparison with 20Z and 20Z-3E strains. The branching of the tricarboxylic acid cycle due to the adenylosuccinate shunt, as well as the presence of malic enzyme, provides metabolic flexibility to M. alcaliphilum, which allows the methanotroph to adapt to a variety of external conditions and, on the other hand, us to modify its genome to obtain valuable products.

While research has extensively investigated the dynamics of CO₂ water partial pressure (pCO₂) and planktonic food webs (PFWs) separately, there has been limited exploration of their potential interconnections, especially in marsh typologies. This study's objectives were to (1) investigated if pCO₂ and atmospheric CO₂ flux can be elucidated by PFW topologies, and (2) ascertain if these potential relationships are consistent across two distinct "Blue Carbon" ecosystems. Abiotic and biotic variables were measured in two contrasting wetlands at the Atlantic French coast: a saltwater (SM, L'Houmeau) and a freshwater marsh (FM, Tasdon). SM acted as a weak carbon source, with pCO₂ between 542 and 842 ppmv. Conversely, FM exhibited strong atmospheric CO₂ source or sink characteristics, varying with seasons and stations, with pCO₂ between 3201 and 114 ppmv. Five PFW topologies were linked to varying pCO₂ across the two ecosystems: three stable topologies ('biological winter', 'microbial', 'multivorous' PFW) exhibited consistently high pCO₂ values (FM: 971, 1136, 3020 ppmv; SM: 'biological winter' not observed, 842, 832 ppmv), while two transient topologies ('weak multivorous' and 'weak herbivorous') displayed lower and more variable pCO₂ values (FM: from 127 to 1402 ppmv; SM: from 638 to 749 ppmv). Seasonality emerged as an influencing factor for both pCO₂ dynamics and PFW. However, PFW in FM did not demonstrate a seasonal equilibrium state, potentially hindering a clearer understanding of the relationship between pCO₂ and PFW. This is the first documented association between PFW topologies and pCO₂ dynamics in "Blue Carbon" marsh environments.

Advancements in nanotechnology, particularly the use of bionanofertilizers, show promise for sustainable agriculture by enhancing soil health and reducing reliance on conventional fertilizers. This study explored the impact of a bioslurry and biogenic zinc oxide (ZnO) nanoparticle formulation on microbial diversity in the rhizosphere of Vigna radiata (mung bean) using 16S rRNA sequencing. High-quality reads from both untreated and treated soil samples revealed a dominance of Archaea, though its proportion was reduced in the treated sample (66% in untreated, 58% in treated). The treated soil showed an increased abundance of beneficial bacterial phyla, including Acidobacteria (+ 6%), Actinobacteria (+ 2%), and Firmicutes (+ 2%). Notably, Acidobacteria-6 and Chloroacidobacteria, essential for nutrient cycling, were enriched in treated soil. Alpha diversity (Chao1 and Shannon indices) was lower in treated samples, indicating selective enhancement of beneficial microbes. Functional analyses like Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) and Statistical Analysis of Taxonomic and Functional Profiles (STAMP) analysis highlighted increased pathways related to motility, chemotaxis, and metabolic processes in the treated soil. These findings suggest that ZnO NPs and bioslurry treatment at 250 ppm improves soil microbial composition and functional attributes, supporting its potential as a bionanofertilizer for soil health restoration and enhanced plant growth.

Can we anticipate the emergence of the next pandemic antibiotic-resistant bacterial clone? Addressing such an ambitious question relies on our ability to comprehensively understand the ecological and epidemiological factors fostering the evolution of high-risk clones. Among these factors, the ability to persistently colonize and thrive in the human gut is crucial for most high-risk clones. Nonetheless, the causes and mechanisms facilitating successful gut colonization remain obscure. Here, we review recent evidence that suggests that bacterial metabolism plays a pivotal role in determining the ability of high-risk clones to colonize the human gut. Subsequently, we outline novel approaches that enable the exploration of microbial metabolism at an unprecedented scale and level of detail. A thorough understanding of the constraints and opportunities of bacterial metabolism in gut colonization will foster our ability to predict the emergence of high-risk clones and take appropriate containment strategies.

Vibrio toranzoniae is a marine bacterium belonging to the Splendidus clade that was originally isolated from healthy clams in Galicia (NW Spain). Its isolation from different hosts and seawater indicated two lifestyles and wide geographical distribution. The aim of the present study was to determine the differences at the genomic level among six strains (4 isolated from clam and 2 from seawater) and to determine their phylogeny. For this purpose, whole genomes of the six strains were sequenced by different technologies including Illumina and PacBio, and the resulting sequences were corrected. Genomes were annotated and compared using different online tools. Furthermore, the study of core- and pan-genomes were examined, and the phylogeny was inferred. The content of the core genome ranged from 2953 to 2766 genes and that of the pangenome ranged from 6278 to 6132, depending on the tool used. Although the strains shared certain homology, with DDH values ranging from 77.10 to 82.30 and values of OrthoANI values higher than 97%, some differences were found related to motility, capsule synthesis, iron acquisition systems or mobile genetic elements. Phylogenetic analysis of the core genome did not reveal a differentiation of the strains according to their lifestyle (commensal or free-living), but that of the pangenome indicated certain geographical isolation in the same growing area. This study led to the reclassification of some isolates formerly described as V. toranzoniae and demonstrated the importance of cured deposited sequences to proper phylogenetic assignment.