International Microbiology最新文献

Plant growth-promoting bacteria (PGPB) play a vital role in enhancing crop productivity by improving nutrient availability, phytohormone production, and stress tolerance. While the individual effects of PGPB and organic matter on plant growth are well-documented, their combined influence remains less explored. This research aimed to investigate the effects of certain plant growth-promoting bacteria belonging to different genera on the growth of Corn when organic matter was added to the soil. Plant growth-promoting properties were measured using conventional methods, and the highest phosphate solubility (42.46 mg/L) and auxin production (3.36 mg/L) were observed in isolate Bacillus 2MDP-10, while the highest release of potassium was measured in isolate Azotobacter 3MDP-4 (6.73 mg/L). A greenhouse experiment was conducted using a factorial, completely randomized design. Results indicated that all measured growth parameters, including fresh and dry weight of roots and shoots, plant height, stem diameter, and chlorophyll index, were significantly higher in inoculated treatments compared to the non-inoculated treatment (negative control). Ensifer sp. 3MDP-1 improved Corn growth more effectively than the positive control. This isolate resulted in a 2.8-fold increase in shoot dry weight, a 2.4-fold increase in root dry weight, a 29% increase in plant height, and a 2.4-fold increase in chlorophyll index relative to the negative control. Our results demonstrated that the addition of organic matter in the form of manure significantly enhanced all measured parameters; however, no significant interaction was observed between manure addition and bacterial inoculation, except for root dry weight and nitrogen percentage. It is likely that bacterial colonization in the rhizosphere and the utilization of carbon released by the roots are key factors responsible for this response.

Streptomyces spp. are widely recognized for their capacity to produce bioactive secondary metabolites, including plant growth regulators such as indole-3-acetic acid (IAA), which have promising applications in sustainable agriculture. Streptomyces californicus represents a relatively unexplored species in terms of auxin biosynthesis. This study aimed to evaluate and optimize IAA production by S. californicus CLV91, assessing its potential as a biostimulant. The isolate CLV91 was identified via whole-genome sequencing and cultivated in ISP2 medium under standard and optimized conditions. IAA quantification was performed using the Salkowski colorimetric method. The impact of culture conditions on auxin synthesis was assessed, and plant growth promotion assays were conducted using Phaseolus vulgaris seeds. Under standard conditions, S. californicus CLV91 synthesized 550 µg mL⁻¹ of IAA, and supplementation with 0.2 g L⁻¹ L-tryptophan increased production by 55.42%, reaching 816 ± 17.26 µg mL⁻¹. Despite the enhanced production, combining all optimized variables led to a reduction in auxin levels, suggesting metabolic stress under cumulative conditions. In plant assays, CLV91-derived auxin significantly increased root elongation, with a maximum effect of 62.7% at 20 µg mL⁻¹. These findings demonstrate the potential of S. californicus CLV91 as a microbial source of auxins for use in biostimulant formulations, supporting its further investigation for field-scale applications in sustainable crop management.

The global aquaculture industry, particularly the farming of Pacific white shrimp (Litopenaeus vannamei), faces significant economic challenges due to infectious diseases, with Vibrio spp. being a primary causative agent of vibriosis. The widespread and often indiscriminate use of antibiotics in aquaculture has led to an alarming increase in antimicrobial resistance (AMR) among Vibrio strains, rendering conventional treatments increasingly ineffective. This study aimed to characterize the phenotypic antibiotic resistance profiles and the presence of associated resistance genes in Vibrio spp. isolates obtained from diseased L. vannamei. Our findings reveal a high prevalence of multidrug-resistant (MDR) Vibrio spp., exhibiting resistance to several commonly used antibiotics, including ampicillin, amoxicillin, doxycycline, tetracycline, erythromycin, azithromycin, dalacin (clindamycin), and cefpodoxime. Molecular analysis identified a high frequency of resistance genes such as Carb, SHV, tetA, floR, sulI, sulII, sulIII, and gryA. Notably, despite widespread phenotypic resistance to ampicillin, the Amp, the amp gene was consistently absent, suggesting alternative or intrinsic resistance mechanisms. A unique and highly unusual finding was the detection of a mecA-homologous gene in Vibrio isolate V28, whose genus identity was confirmed by 16S rRNA sequencing. The pervasive nature of AMR in these Vibrio isolates underscores the urgent need for sustainable alternative strategies, such as bacteriophage therapy. This characterization provides critical foundational data essential for the future development of such targeted interventions.

Garlic (Allium sativum L.) is a high-value horticultural crop whose bulbs provide a unique ecological niche for specialized endophytic microbiota. Despite their potential as microbial reservoirs for plant health and biocontrol, these endophytes remain poorly studied, particularly within clove meristems. This study investigated the cultivable endophytic communities from clove meristems of ten Mexican garlic varieties. A total of 119 bacterial isolates, belonging to 14 genera, and 38 fungal isolates, grouped into 2 genera, were obtained. The bacteria exhibited key functional traits, including nutrient solubilization, nitrogen fixation, and hydrolytic enzyme production, with most strains significantly promoting the growth of garlic explants. In contrast, the isolated fungi (Fusarium and Penicillium) proved pathogenic. In antagonism assays, Paenibacillus sp. MP10 and Rhodococcus sp. MP3 showed high inhibition (65.38-94.74%) against the tested fungal strains. In garlic germination assays, Pseudomonas sp. 1JPC and Enterobacter sp. 2AMTX, 2APTE, and 4AMTX increased root length 2-fourfold, root number 3-fourfold, and fresh weight approximately onefold. In maize bioassays, Phytobacter sp. 5AMCH94, Pseudomonas sp. 1APCY, and Paenibacillus sp. H1 enhanced seedling area by 20-60%, seedling length by 10-30%, root number by 30-140%, and dry weight by 40-50%. Furthermore, 16S rRNA sequencing revealed that inoculation with Paenibacillus sp. H1 increased endophytic bacterial diversity and the relative abundance of Comamonadaceae and Lactobacillaceae. These findings highlight the value of garlic meristems as reservoirs for microbial bioinoculant development and the recovery of conserved varieties.

Chronic hyperglycemia in diabetic patients promotes Staphylococcus aureus colonization and biofilm formation, contributing to persistent infection and poor wound healing in diabetic foot ulcers (DFUs). Biofilms hinder antibiotic penetration and promote resistance, highlighting the need for targeted anti-biofilm strategies. In this study, domain antibody-displaying M13 phages were developed to selectively target S. aureus biofilms. Among the selected clones, A7-displayed phage showed the strongest binding to S. aureus based on indirect ELISA and exhibited potent, dose-dependent inhibition of biofilm formation without affecting bacterial viability. This non-bactericidal, anti-virulence effect was associated with a significant reduction in staphyloxanthin production, a pigment linked to oxidative stress resistance. Quantitative RT-PCR analysis further revealed that A7 and C1 downregulated the expression of icaA, a key gene involved in biofilm matrix synthesis. Despite its efficacy, checkerboard synergy testing showed that combining A7-displayed phage with ampicillin resulted in an antagonistic interaction (FICI > 4), suggesting that A7 is most effective as a standalone anti-biofilm agent. Target identification using far-western blotting and MS/MS analysis revealed that A7 binds specifically to a cadmium-transporting ATPase, and molecular docking analysis showed A7 interaction with the C-terminal helical domain of CadA, potentially affecting cadmium efflux and oxidative stress homeostasis. This disruption may underlie the observed biofilm inhibition. These findings establish A7-displayed phage as a promising, non-cytotoxic biotherapeutic targeting S. aureus biofilms, offering a novel strategy for DFU management and other chronic infections where conventional antibiotics fall short.

Pseudomonas aeruginosa is a multidrug-resistant (MDR) pathogen. It causes life-threatening diseases through quorum sensing (QS)-associated virulence. Thus, the attenuation of QS may be an effective strategy to combat the pathogen. In this study, Shewanella indica SU1 isolated from the marine environment showed QS inhibitory activity against biosensor strain Chromobacterium violaceum MTCC 2656. The lead compound was purified and tentatively identified as eicosyl heptafluorobutyrate (EPB). P. aeruginosa MCC 3457 was treated with EPB, and results revealed a reduced production of pyocyanin (79%), rhamnolipids (54%), exopolysaccharide (60%), and biofilm (66%). The motility was greatly affected in EPB-treated cultures. In an in silico approach, EPB exhibited good binding interactions and stability with the target protein LasR. The pharmacokinetics studies divulged that EPB, the lead compound, can be a good drug candidate. This is the first report on the QS inhibitory activity of S. indica SU1 and EPB as an anti-QS compound.

This study investigates the impact of a defined starter culture on the fermentation of cocoa beans and its influence on the production of volatile and non-volatile compounds related to sensory quality. A microbial consortium comprising Saccharomyces cerevisiae, Pichia kudriavzevii, Levilactobacillus brevis, and Acetobacter okinawensis was selected based on their enzymatic activity and acid regulation properties. Fermentation trials showed that the starter culture enhanced the synthesis of key volatile compounds, particularly esters and higher alcohols, such as 2-phenylethanol and 2-phenylethyl acetate, which contribute floral and fruity aromas. Compared to artisanal fermentation, treatments with starter cultures exhibited lower levels of lactic and acetic acids and an increase in succinic acid, indicating a balanced acid profile and potential metabolic synergy between inoculated and native microbiota. The study also identified specific volatile compounds as potential biochemical markers to monitor fermentation progress. These findings support the application of functional starter cultures to standardize and improve cocoa fermentation, offering opportunities to enhance quality and value in small-scale production systems.

An endophytic bacterium having the capability to produce biosurfactant was isolated from the root gall of Lady's finger (Abelmoschus esculentus). The stain reduces the surface tension of the culture media from 50.8mN to 30.8mN in 24 h and produces 3.3 g/L of biosurfactant at 48 h of incubation using glucose as a carbon source. It was revealed from the characterization of the biosurfactant that the strain produces a lipopeptide type of biosurfactant and the main component of the lipopeptide was surfactin. The bacterial strain was further characterized through molecular technique and identified as Providencia vermicola which was designated as strain SCL1. The biosurfactant produced by the strain was found to exhibit efficient antifungal activities against phytopathogenic fungi Colletotrichum gleoisporoides, Sclerotinium sclerotiorum, and Corynespora cassicolla. This is the first report that an endophytic bacterium Providencia vermicola can produce lipopeptide biosurfactant having antifungal properties against certain phytopathogenic fungi.

This research aimed to identify native biocontrol bacteria capable of suppressing Phytophthora infestans in potato crops. A total of forty bacterial strains were isolated from wheat (Triticum aestivum), sunflower (Helianthus annuus), potato (Solanum tuberosum), and cotton (Gossypium herbaceum) plants collected in Sibi, Pakistan. Out of these, ten isolates showed antagonistic effects against P. infestans, with inhibition percentages ranging from 27 to 62%. The isolate WL2.3 exhibited the strongest inhibition at 62%. Furthermore, sporangia germination tests, including those using cell-free supernatants, revealed that WL2.3 and its supernatant inhibited sporangia germination by 65% and 60%, respectively. Strain WL2.3 also showed various traits that promoted growth in plants, including solubility of phosphate, siderophores, ability to synthesize indole-3-acetic acid, cellulose lysis, and generation of hydrogen cyanide. The phylogenetic analysis based on 16S rRNA demonstrated a match of 98.80% with Bacillus subtilis with the GenBank accession number of PQ764123.1. The efficacy of WL2.3 was also experimented in pot experiments to determine its agronomic and pathological effects to potato plants infested with P. infestans. Of the 11 parameters that were considered, eight of them showed a significant improvement: percentage disease index, number of tubers, weight of tubers, length of the shoot, number of leaves, weight of roots, number of roots, and number of shoots. These results indicate that WL2.3 successfully reduced the effects of the oomycete pathogen, as shown by a decrease in the percentage disease index to 46% in the group treated with WL2.3. Thus, WL2.3 is a promising biocontrol agent for plant disease management and growth promotion.