International Microbiology最新文献

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.

Olive trees are susceptible to various diseases, notably root rot caused by Pythium spp., which presents significant challenges to cultivation. Conventional chemical control methods have limitations, necessitating exploration of eco-friendly alternatives like biological control strategies. This study aims to evaluate the potential of rhizobacteria in managing Pythium schmitthenneri-induced root rot in olive trees. We screened 140 bacteria isolated from olive tree rhizospheres for antifungal activity against the pathogen in vitro. Twelve isolates exhibited promising antifungal activity, identified through 16S rDNA gene sequencing as primarily Bacillus, Pseudomonas, Stenotrophomonas, and Alcaligenes species. Particularly, Pseudomonas koreensis (A28 and A29), Pseudomonas reinekei (A16), and Bacillus halotolerans (A10) were the highest effective strains. Mechanistic investigations revealed positive protease production in all twelve isolates, with eight producing amylase and cellulase. Chitinase activity was absent, while five solubilized tricalcium phosphate. Furthermore, eight secreted hydrocyanic acid (HCN), ten synthesized indole-3-acetic acid (IAA), and nine produced siderophores. Variability existed in antimicrobial substance production, including bacillomycin (seven isolates), iturin (eleven isolates), fengycin (two isolates), and surfactin (three isolates). Plant growth-promoting rhizobacteria (PGPR) capabilities were assessed using canola (Brassica napus) seedlings, showing enhanced growth in treated seedlings compared to controls. Greenhouse experiments confirmed the biocontrol efficacy of P. koreensis A28 and Bacillus subtilis C6 against root rot disease. These findings suggest these strains could serve as promising tools for managing olive tree root rot, offering a sustainable alternative to hazardous agrochemicals.

Enterobacteriaceae are significant opportunistic pathogens in the environment, impacting both biological and human health. The rise in antibiotic-resistant strains has compelled the exploration of bacteriophages as alternative biological control agents. In this study, we isolated a bacteriophage JgK1 specific to Escherichia coli from environmental samples. This bacteriophage can effectively lyse Escherichia coli jg1, exhibiting an optimal MOI of 0.01 and an average mutation rate of 1.96 × 10^-7. One-step growth curve analysis revealed an incubation period of 25 min and a release amount of approximately 430.75 pfu/infection center. It can withstand high temperatures of 55 °C. Additionally, whole genome sequencing (WGS) confirmed a genome size of 74,059 bp, containing 107 open reading frames (ORF), with no virulence or resistance-related genes, nor lysogenic genes. Comparative genomic analysis indicated lower coverage compared to other known isolated bacteriophages, with the highest coverage being 72%. This study suggests that bacteriophage JgK1 has the potential to serve as an effective biological control antibacterial agent, offering a promising alternative to antibiotics for managing Escherichia coli infections.

Background: With the increasing indications for fecal microbiota transplantation for the treatment of diseases, there is a growing demand for the preparation of frozen or lyophilized fecal microbiota products that are viable and can stably colonize the recipient. The addition of protective agents plays an important role in the preparation. However, there has been no systematic evaluation of the protective agents used in fecal microbiota sample transplantation preparation for transplantation.

Methods: We were used the donor bacterial flora containing 10 different formulations of protective agents were frozen, lyophilized, and stored. Plate counting, CCK8 assay, flow cytometry after LIVE/DEAD staining, and fluorescence intensity were used to assess viable bacteria in vitro. In addition, the donor bacterial flora samples containing different formulations protective agents were transplanted into antibiotic-treated SPF mice, with 3 mice in each group and a total of 5 groups. Fecal samples were collected for metagenomic sequencing to observe the colonization of the bacterial flora in the recipient mice.

Results: The preliminary screening results showed that the survival rate of bacteria in the 5% trehalose (T) groups, and 5% sucrose, 5% inulin, and 1% cysteine hydrochloride (SI) groups was slightly higher than that in the other groups. SI groups tended to be more protective against anaerobes than T groups. The donor gut microbiota containing the SI groups protective agent exhibited the best colonization of the recipient mice. The protective effects of different formulations of protective agents on the colonized probiotic strains and the metabolic function of the bacterial flora in recipient mice were found to be species specific.

Conclusions: SI groups can not only better protect the activity of anaerobic bacteria in the intestine, but also effectively promote the effective colonization of donor intestinal bacteria in the recipient mice, and the effect of frozen storage method is less, and can be used at the same time as frozen and freeze-dried preparation. It can be used as a reference for the selection of protective agents in the preparation of fecal microbiota transplantation samples.

The kefir granules are a microbial consortium with numerous properties, among which their antifungal action has been reported. The aim of this research was to evaluate the antifungal capacity of yeasts isolated from kefir against Fusarium graminearum for its possible application as biocontrol agents. The inhibition of fungal growth was analyzed, according to dual tests, and the production of volatile organic compounds. The inhibition of the production of the mycotoxin deoxynivalenol was also analyzed. The six isolates studied belonged to the species Geotrichum candidum (2), Saccharomyces cerevisiae (1), Pichia kudriavzevii (2), and Pichia membranifaciens (1). They were isolated from kefir and identified in a previous work. The yeasts tested produced a reduction in the growth of F. graminearum in all assays. In particular, three of the isolates, 1 belonging to the species S. cerevisiae and 2 to the species P. kudriavzevii, generated volatile organic compounds that significantly inhibited the growth of the fungus in a 49.61, 51.46, and 49.61%, respectively. The yeasts produced an inhibition of the mycotoxin deoxynivalenol correlated with a reduction in the growth of the fungus. The isolates of Geotrichum candidum (Gc30) and Pichia kudriavzevii (Pk27, PK20) significantly reduced the deoxynivalenol content of F. graminearum by 86, 89, and 88%, and the growth inhibition in the assay was 34, 61, and 48%, respectively. The data obtained about yeasts of novel origin are promising for their possible use as fungal biocontrol agents in foods as an alternative to agrochemicals.

The study of the microbial community of wells is a methodologically complex, but urgent problem. In the course of our work, five samples of oil wells were selected from one deposit of the Romashkino field. The samples were subjected to nucleic acid extraction using three methods-direct DNA extraction, and after enrichment using aerobic and anaerobic cultivation methods. In three samples from wells W1-W3, extraction after anaerobic enrichment was successful. Effective aerobic cultivation was possible in all five samples. All three of these samples represented the aqueous part of the produced fluid; samples from wells W4 and W5, where extraction was difficult, represented the oil part. During the analysis of the microbial community in enrichment cultures from wells W1-W3, exogenous microorganisms such as Desulfovibrio, Acetobacterium, Bacillus, and Georgenia were discovered, which can be explained by the long-term exploitation of this section of the field. In one sample from well W1, community information was obtained using direct extraction and anaerobic enrichment. It was found that the microbial community changed significantly after enrichment, and its diversity decreased. At the same time, however, the functional profile of microorganisms has not changed, and sulfate-reducing microorganisms dominate in both samples. Thus, the results of the work allow us to make an assumption about the physicochemical parameters of samples in which the study of the microbial community is possible. In addition, it became known that well W1 needs to control the process of biological acidification and has a high risk of equipment corrosion.

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.

Cultivable microbial communities associated with plants inhabiting extreme environments have great potential in biotechnological applications. However, there is a lack of knowledge about these microorganisms from Bryophyllum pinnatum (which survives in severely barren soil) and their ability to promote plant growth. The present study focused on the isolation, identification, biochemical characterization, and potential applications of root endophytic bacteria and rhizosphere bacteria. A total of 73 bacterial isolates were obtained, with 50 derived from rhizospheric soil and 23 from root tissue. The identified strains were categorized into 16 genera, with Bacillus, Priestia, Pseudarthrobacter, Neobacillus, Mesobacillus, and Arthrobacter being the most species-rich genera. Heat stress experiments indicated that almost half (50.7%) of the selected isolates were tolerant to heat stress. Furthermore, most strains present diverse capabilities for biotechnological applications, including the potential for indole-3-acetic acid (IAA) production, organic phosphorus solubilization, inorganic phosphorus solubilization, and nitrogen fixation. Some isolates (21.92%) exhibited broad-spectrum antagonistic activity against various phytopathogenic fungi, including Fusarium spp. Agar plate assays revealed that the Cellulomonas hominis strain LS43 and Bacillus inaquosorum strain LS77 significantly increased the total fresh weight of Arabidopsis (P < 0.05), yet these strains did not significantly affect the primary root length or the number of leaves. Notably, a subset of the strains tested did not significantly increase the growth of Arabidopsis and, in fact, had inhibitory effects on certain growth parameters. This is the first investigation highlighting the potential of root endophytic bacteria and rhizosphere bacteria in association with B. pinnatum in barren soils. Thus, these isolated strains positively influence plant nutrient uptake, stress resilience, and biocontrol to reduce chemical inputs in conventional agricultural practices, highlighting the importance of their development as biofertilizers for improving the quality of barren soil.

In agricultural areas of arid Xinjiang, China, selecting appropriate irrigation strategies for farmland is essential. Increasing attention is being paid to the ecological effects of different irrigation methods on the soil environment. As a crucial component of soil quality, the microbial community is a key indicator of the impacts of irrigation on the soil environment. To investigate the effects of irrigation treatments on the properties of rhizosphere soil and the underlying microbial community characteristics, this study conducted an alfalfa field experiment applying three water-saving treatments (3750, 4500, and 5250 m³ hm^-2) and regular irrigation (6750 m³ hm^-2, CK). The results showed that the water-saving treatments increased the soil pH, salinity, available nitrogen, and phosphorus levels. The water-saving treatments decreased the richness and diversity of the bacterial community in the rhizosphere but increased those of the fungal community. The influence of stochastic processes on fungal and bacterial communities assembly under water-saving treatments was more noticeable than that under CK. Compared with CK, water-saving treatments reduced the complexity of microbial network and increased the potential negative interaction between bacteria and fungi. Functional prediction analysis showed that species specificity among treatments may result from a specific selection of rhizosphere functional requirements. This study reveals the effect of controlling irrigation quantity on protecting soil microbial diversity and function and improves the understanding of rhizosphere soil community response affected by different irrigation strategies. The results facilitate the development of effective and beneficial agricultural measures.