Strain B2 Research Articles

Molecular screening of bacteriocin-producing Bacillus spp. isolated from Soumbala, a fermented food condiment from Parkia biglobosa seeds

Bacteriocin-producing Bacillus species have an attractive interest as less studied spore-forming probiotics for food production. In this study, 20 strains of Bacillus were isolated from soumbala, a local fermented food condiment from Burkina Faso. They were characterized based on phenotype, antibacterial activity against Listeria monocytogenes NTCT983 and genotypic analysis by PCR, using specific primers for Bacillus sp., B. subtilis group, B. cereus group, bacteriocin genes, subtilin gene (spaS) and subtilosin gene (sboA). All the isolates were presumptively identified as Bacillus spp. with predominance of B. subtilis species (30%). Out of 20 strains, 11 showed anti-Listeria activity, with inhibition zones ranging from 11.12±0.53 mm (strain B21) to 25.25±0.35 mm (strain F25). PCR profiles revealed that 18 strains belonged to the B. subtilis group while O28 and O46 belonged to the B. cereus species. In addition, 13 strains carried bacteriocin genes, 10 possessed gene sboA and only strain O48 carried gene spaS. This finding highlights the predominance of bacteriocin-producing B. subtilis group species in Soumbala production population. These could be further characterized as probiotic starter cultures carrier for controlled production of high-quality soumbala.

Screening and Identification of Yeasts Strains of Degradable Organic Acids in Lonicera edulis

Microorganisms were isolated and purified from the fresh fruit of Changbai Mountain. The yeasts strains of degradable organic acids were screened and obtained. The acid reducing characteristics and tolerance were studied, and the biological identification was carried out. The results showed that five strains with acid reducing effect were selected from the fruits of Lonicera edulis. The acid reducing rates of B5 for malic acid, citric acid and tartaric acid were 42.60%±0.85%, 18.28%±0.80% and 13.09%±0.61% respectively. The strain B5 was identified as zygosasaccharomyces bisporus by morphological observation, physiological and biochemical tests and 26S rDNA identification. The tolerant to glucose and SO2 concentrations of 250 g/L and 400 mg/L and alcohol tolerance of 18% vol, respectively. The results of this experiment can provide a reference for the biological deacidification of fruit wine products.

BLB8, an antiviral protein from Brevibacillus laterosporus strain B8, inhibits Tobacco mosaic virus infection by triggering immune response in tobacco

Tobacco mosaic virus (TMV) is one of destructive plant viruses, causing serious economic losses in the world. Using antiviral proteins or elicitors to inhibit viral infection or promote plant immunity is one of the efficient strategies against TMV. Our previous study identified that the fermentation broth of Brevibacillus laterosporus strain B8 showed strong antiviral activity against TMV. However, the active antiviral ingredient is still unclear. Here, BLB8 (B. laterosporus strain B8 protein, BLB8), an antiviral protein from B. laterosporus strain B8 was isolated and characterized. BLB8 showed protective, inactive and curative effects against TMV, and the inhibition rate reached up to 63%, 83% and 55%, respectively. BLB8 infiltrated around the infection site of the recombinant virus TMV-GFP inhibited the systemic extend and movement of TMV. Pretreatment of the bottom leaves with BLB8 inhibited the spread and accumulation of TMV in upper systemic leaves. Furthermore, BLB8 caused hypersensitive response (HR) in a dose-dependent way, promoted H2 O2 accumulation, and induced the expression of defense-relative genes in Nicotiana benthamiana. The antiviral protein BLB8 from B. laterosporus strain B8 effectively inhibits TMV infection in inactivation, protective and curative effects through triggering plant immunity in tobacco. Therefore, the present study provides a new antiviral agent for prevention and control of viral disease. © 2021 Society of Chemical Industry.

Dietary supplementation of Bacillus velezensis B8 enhances immune response and resistance against Aeromonas veronii in grass carp

The heavy use of prophylactic antibiotics in aquaculture leads to elevated antibiotic residues, posing a huge hidden danger in aquaculture products and other natural aquatic environments. Therefore, this study aims to isolate probiotics that can replace antibiotics from the gut of grass carp for disease control. Bacillus velezensis B8 was isolated from the gut of grass carp and showed broad-spectrum antimicrobial activity against several fish pathogenic bacteria, including Aeromonas hydrophilis, Aeromonas veronii, Vibrio parahaemolyticus, Escherichia coli, Edwardsiella tarda and Vibrio mimicus. The safety evaluation showed that the strain B8 was non-toxic to grass carp, had no hemolytic activity, and was sensitive to most antibiotics. In vitro study indicated that strain B8 was viable at pH 2–7, had weak tolerance to 0.1% (w/v) bile salt, and could grow at 10°C–40 °C. The grass carps were fed with diets containing 0 (control), 107, and 109 cfu/g of strain B8 for 4 weeks. Various immune parameters were measured at 1, 2, 3, and 4 weeks of post-feeding. The results of non-specific immunoassay showed that diets supplemented with B8 significantly increased alkaline phosphatase (AKP) and superoxide dismutase (SOD) activity in serum samples (p < 0.05). The expression levels of immune-related genes in the kidney and spleen of grass carp were measured. Among them, the expression levels of IgM and TNF-α both in spleen and kidney were significantly increased after 3 and 4 weeks of post-feeding (p < 0.05). The expression of IgD and MHCI in kidney was significantly upregulated in high-dose groups after 2 and 3 weeks of feeding, respectively (p < 0.05). In addition, after 7 days of challenging with A. veronii, the high-dose group and low-dose group had 48% and 53% survival compared to 25% survival for the control group. These results suggest that B. velezensis B8 has the potential to be developed into a microecological preparation for the alternatives of antibiotics in aquaculture.

Coinducible Catabolism of 1-Naphthol via Synergistic Regulation of the Initial Hydroxylase Genes in Sphingobium sp. Strain B2.

1-Naphthol, a widely used raw material for organic synthesis, is also a well-known organic pollutant. Due to its high toxicity, 1-naphthol is rarely used by microorganisms as the sole carbon source for growth. In this study, catabolism of 1-naphthol by Sphingobium sp. strain B2 was found to be greatly enhanced by additional supplementation with primary carbon sources (e.g., glucose, maltose, and sucrose), and 1-naphthol was even used as the carbon source for growth when strain B2 cells had been preinduced by both 1-naphthol and glucose. A distinct two-component flavin-dependent monooxygenase, NdcA1A2, was found to be responsible for the initial hydroxylation of 1-naphthol to 1,2-dihydroxynaphthalene, a more toxic compound. Transcriptional levels of ndcA1A2 genes were significantly upregulated when strain B2 cells were cultured with both 1-naphthol and glucose compared to cells cultured with only 1-naphthol or glucose. Two transcriptional regulators, the activator NdcS and the inhibitor NdcR, were found to play key roles in the synergistic regulation of the transcription of the 1-naphthol initial catabolism genes ndcA1A2IMPORTANCE Cometabolism is a widely observed phenomenon, especially in the field of microbial catabolism of highly toxic xenobiotics. However, the mechanisms of cometabolism are ambiguous, and the roles of the obligately coexisting growth substrates remain largely unknown. In this study, we revealed that the roles of the coexisting primary carbon sources (e.g., glucose) in the enhanced catabolism of the toxic compound 1-naphthol in Sphingobium sp. strain B2 were not solely because they were used as growth substrates to support cell growth but, more importantly, because they acted as coinducers to interact with two transcriptional regulators, the activator NdcS and the inhibitor NdcR, to synergistically regulate the transcription of the 1-naphthol initial catabolism genes ndcA1A2 Our findings provide new insights into the cometabolic mechanism of highly toxic compounds in microorganisms.

A biological agent modulates the physiology of barley infected with Drechslera teres

Recognized as the causal agent of net blotch, Drechslera teres is responsible for major losses of barley crop yield. The consequences of this leaf disease are due to the impact of the infection on the photosynthetic performance of barley leaves. To limit the symptoms of this ascomycete, the use of beneficial bacteria known as “Plant Growth Promoting Rhizobacteria” constitutes an innovative and environmentally friendly strategy. A bacterium named as strain B25 belonging to the genus Burkholderia showed a strong antifungal activity against D. teres. The bacterium was able to limit the development of the fungus by 95% in detached leaves of bacterized plants compared to the non-bacterized control. In this study, in-depth analyses of the photosynthetic performance of young barley leaves infected with D. teres and/or in the presence of the strain B25 were carried out both in and close to the necrotic area. In addition, gas exchange measurements were performed only near the necrotic area. Our results showed that the presence of the beneficial bacterium reduced the negative impact of the fungus on the photosynthetic performance and modified only the net carbon assimilation rate close to the necrotic area. Indeed, the presence of the strain B25 decreased the quantum yield of regulated non-photochemical energy loss in PSII noted as Y(NPQ) and allowed to maintain the values stable of maximum quantum yield of PSII photochemistry known as Fv/Fm and close to those of the control in the presence of D. teres. To the best of our knowledge, these data constitute the first study focusing on the impact of net blotch fungus and a beneficial bacterium on photosynthesis and respiratory parameters in barley leaves.

Integration of pre-colonized and mediator immobilized mixed culture for the improvement of electricity production of microbial fuel cells

In this study, we have immobilized bacterial cells with mediators as bioaugmentation to increase the numbers of bacterial cells in anodic biofilm for better microbial fuel cell (MFC) performance. Four individual bacterial strains (strain E1, strain SCS5, strain B2 and Shewanella putrefaciens) and their mixed culture were first evaluated for electricity production in MFCs. The mixed culture MFC produced higher power density (3.021 Wm−3) than pure strains. The pre-colonized (PC) biofilms together with mediator immobilized mixed culture (MIMC) beads as bioanodes further enhanced the performance of MFCs. Integrated PC/MIMC MFCs containing anthraquinine-2,6-disulfonate (AQDS) and Fe3O4 immobilized mixed culture beads produced 1.50 and 1.47 times power density with respect to mixed culture biofilm, respectively. AQDS immobilization showed better performance compared to Fe3O4 in energy output. The integrated use of PC biofilms and MIMC exhibited lower charge transfer resistance than corresponding individual anode biofilms in MFCs according to electrochemical impedance spectroscopy analysis. The MFC having PC/MIMC as anode showed the ability to store electrons generated by bacteria, but the biocapacitance of anode was altered after integrating MIMC bead particles. Thus, the collective use of PC biofilm and MIMC beads will be one of the potential choices for improving MFC performance.

A bifunctional enzyme belonging to cytochrome P450 family involved in the O-dealkylation and N-dealkoxymethylation toward chloroacetanilide herbicides in Rhodococcus sp. B2

BackgroundThe chloroacetamide herbicides pretilachlor is an emerging pollutant. Due to the large amount of use, its presence in the environment threatens human health. However, the molecular mechanism of pretilachlor degradation remains unknown.ResultsNow, Rhodococcus sp. B2 was isolated from rice field and shown to degrade pretilachlor. The maximum pretilachlor degradation efficiency (86.1%) was observed at a culture time of 5 d, an initial substrate concentration 50 mg/L, pH 6.98, and 30.1 °C. One novel metabolite N-hydroxyethyl-2-chloro-N-(2, 6-diethyl-phenyl)-acetamide was identified by gas chromatography-mass spectrometry (GC–MS). Draft genome comparison demonstrated that a 32,147-bp DNA fragment, harboring gene cluster (EthRABCDB2), was absent from the mutant strain TB2 which could not degrade pretilachlor. The Eth gene cluster, encodes an AraC/XylS family transcriptional regulator (EthRB2), a ferredoxin reductase (EthAB2), a cytochrome P450 monooxygenase (EthBB2), a ferredoxin (EthCB2) and a 10-kDa protein of unknown function (EthDB2). Complementation with EthABCDB2 and EthABDB2, but not EthABCB2 in strain TB2 restored its ability to degrade chloroacetamide herbicides. Subsequently, codon optimization of EthABCDB2 was performed, after which the optimized components were separately expressed in Escherichia coli, and purified using Ni-affinity chromatography. A mixture of EthABCDB2 or EthABDB2 but not EthABCB2 catalyzed the N-dealkoxymethylation of alachlor, acetochlor, butachlor, and propisochlor and O-dealkylation of pretilachlor, revealing that EthDB2 acted as a ferredoxin in strain B2. EthABDB2 displayed maximal activity at 30 °C and pH 7.5.ConclusionsThis is the first report of a P450 family oxygenase catalyzing the O-dealkylation and N-dealkoxymethylation of pretilachlor and propisochlor, respectively. And the results of the present study provide a microbial resource for the remediation of chloroacetamide herbicides-contaminated sites.

Genomic Sequence Resource of Alternaria alternata Strain B3 Causing Leaf Blight on Ophiopogon japonicus.

Black spot of Ophiopogon japonicus is an economically important disease, which can result in significant losses of both yield and quality of this traditional Chinese medicinal plant. The disease is caused by the small-spored fungal pathogen Alternaria alternata, a necrotrophic fungus that is ubiquitously distributed in the environment. Here, we present the draft whole-genome sequence of A. alternata strain B3 that caused black spot on O. japonicus. The assembly consists of 76 contigs with an estimated genome size of 33.8 Mb. Furthermore, we identified genes that may be associated with the pathogenicity, such as carbohydrate-active enzymes, secreted proteins, and secondary metabolite gene clusters. This genome resource will provide a useful source for future research on the evolution of pathogenicity of A. alternata and phylogenomic analysis in delineating phylogenetic lineages within the genus Alternaria.

Comparative transcriptional analyses of Pleurotus ostreatus mutants on beech wood and rice straw shed light on substrate-biased gene regulation.

Distinct wood degraders occupying their preferred habitats have biased enzyme repertoires that are well fitted to their colonized substrates. Pleurotus ostreatus, commonly found on wood, has evolved its own enzyme-producing traits. In our previous study, transcriptional shifts in several P. ostreatus delignification-defective mutants, including Δhir1 and Δgat1 strains, were analyzed, which revealed the downregulation of ligninolytic genes and the upregulation of cellulolytic and xylanolytic genes when compared to their parental strain 20b on beech wood sawdust medium (BWS). In this study, rice straw (RS) was used as an alternative substrate to examine the transcriptional responses of P. ostreatus to distinct substrates. The vp1 gene and a cupredoxin-encoding gene were significantly upregulated in the 20b strain on RS compared with that on BWS, reflecting their distinct regulation patterns. The overall expression level of genes encoding glucuronidases was also higher on RS than on BWS, showing a good correlation with the substrate composition. Transcriptional alterations in the mutants (Δhir1 or Δgat1 versus 20b strain) on RS were similar to those on BWS, and the extracellular lignocellulose-degrading enzyme activities and lignin-degrading ability of the mutants on RS were consistent with the transcriptional alterations of the corresponding enzyme-encoding genes. However, transcripts of specific genes encoding enzymes belonging to the same CAZyme family exhibited distinct alteration patterns in the mutant strains grown on RS compared to those grown on BWS. These findings provide new insights into the molecular mechanisms underlying the transcriptional regulation of lignocellulolytic genes in P. ostreatus.Key Points• P. ostreatus expressed variable enzymatic repertoire-related genes in response to distinct substrates.• A demand to upregulate the cellulolytic genes seems to be present in ligninolysis-deficient mutants.• The regulation of some specific genes probably driven by the demand is dependent on the substrate.

CaNRT2.1 Is Required for Nitrate but Not Nitrite Uptake in Chili Pepper Pathogen Colletotrichum acutatum

Chili peppers are an important food additive used in spicy cuisines worldwide. However, the yield and quality of chilis are threatened by anthracnose disease caused by Colletotrichum acutatum. Despite the impact of C. acutatum on chili production, the genes involved in fungal development and pathogenicity in this species have not been well characterized. In this study, through T-DNA insertional mutagenesis, we identified a mutant strain termed B7, which is defective for the growth of C. acutatum on a minimal nutrient medium. Our bioinformatics analysis revealed that a large fragment DNA (19.8 kb) is deleted from the B7 genome, thus resulting in the deletion of three genes, including CaGpiP1 encoding a glycosylphosphatidyl-inisotol (GPI)-anchored protein, CaNRT2.1 encoding a membrane-bound nitrate/nitrite transporter, and CaRQH1 encoding a RecQ helicase protein. In addition, T-DNA is inserted upstream of the CaHP1 gene encoding a hypothetical protein. Functional characterization of CaGpiP1, CaNRT2.1, and CaHP1 by targeted gene disruption and bioassays indicated that CaNRT2.1 is responsible for the growth-defective phenotype of B7. Both B7 and CaNRT2.1 mutant strains cannot utilize nitrate as nitrogen sources, thus restraining the fungal growth on a minimal nutrient medium. In addition to CaNRT2.1, our results showed that CaGpiP1 is a cell wall-associated GPI-anchored protein. However, after investigating the functions of CaGpiP1 and CaHP1 in fungal pathogenicity, growth, development and stress tolerance, we were unable to uncover the roles of these two genes in C. acutatum. Collectively, in this study, our results identify the growth-defective strain B7 via T-DNA insertion and reveal the critical role of CaNRT2.1 in nitrate transportation for the fungal growth of C. acutatum.

Effect of Metabolites Produced by Bacillus atrophaeus and Brevibacterium frigoritolerans Strains on Postharvest Biocontrol of Alternaria alternata in Tomato (Solanum lycopersicum L.).

In the present study, the antifungal activity of metabolites produced by Bacillus atrophaeus B5 and a new Brevibacterium strain against Alternaria alternata was evaluated. Assays in vitro and in vivo on tomato fruit during postharvest were made. Based on the 16S rDNA gene sequence analysis, the new strain (strain B7) was identified as Brevibacterium frigoritolerans. Metabolites produced by both bacterial strains reduced the spore germination of A. alternata in vitro and decreased the severity of the alternaria rot disease on tomato fruit during postharvest. This is the first report that demonstrates the potential of B. frigoritolerans B7 as a biocontrol agent against this fungal phytopathogen. The use of metabolites produced by B. atrophaeus B5 and B. frigoritolerans B7 represents a new approach to reduce the use of chemical pesticides and control fungal decay during the postharvest stage.

Genomic and Physiological Properties of a Facultative Methane-Oxidizing Bacterial Strain of Methylocystis sp. from a Wetland.

Methane-oxidizing bacteria are crucial players in controlling methane emissions. This study aimed to isolate and characterize a novel wetland methanotroph to reveal its role in the wetland environment based on genomic information. Based on phylogenomic analysis, the isolated strain, designated as B8, is a novel species in the genus Methylocystis. Strain B8 grew in a temperature range of 15 °C to 37 °C (optimum 30–35 °C) and a pH range of 6.5 to 10 (optimum 8.5–9). Methane, methanol, and acetate were used as carbon sources. Hydrogen was produced under oxygen-limited conditions. The assembled genome comprised of 3.39 Mbp and 59.9 mol% G + C content. The genome contained two types of particulate methane monooxygenases (pMMO) for low-affinity methane oxidation (pMMO1) and high-affinity methane oxidation (pMMO2). It was revealed that strain B8 might survive atmospheric methane concentration. Furthermore, the genome had various genes for hydrogenase, nitrogen fixation, polyhydroxybutyrate synthesis, and heavy metal resistance. This metabolic versatility of strain B8 might enable its survival in wetland environments.

A Crosstalk Between Brachypodium Root Exudates, Organic Acids, and Bacillus velezensis B26, a Growth Promoting Bacterium.

Plant growth-promoting rhizobacteria (PGPR) are associated with plant roots and use organic compounds that are secreted from root exudates as food and energy source. Root exudates can chemoattract and help bacteria to colonize the surface of plant roots by inducing chemotactic responses of rhizospheric bacteria. In this study, we show that root colonization of Brachypodium distachyon by Bacillus velezensis strain B26 depends on several factors. These include root exudates, organic acids, and their biosynthetic genes, chemotaxis, biofilm formation and the induction of biofilm encoding genes. Analysis of root exudates by GC-MS identified five intermediates of the TCA cycle; malic, fumaric, citric, succinic, oxaloacetic acids, and were subsequently evaluated. The strongest chemotactic responses were induced by malic, succinic, citric, and fumaric acids. In comparison, the biofilm formation was induced by all organic acids with maximal induction by citric acid. Relative to the control, the individual organic acids, succinic and citric acids activated the epsD gene related to EPS biofilm, and also the genes encoding membrane protein (yqXM) and hydrophobin component (bslA) of the biofilm of strain B26. Whereas epsA and epsB genes were highly induced genes by succinic acid. Similarly, concentrated exudates released from inoculated roots after 48 h post-inoculation also induced all biofilm-associated genes. The addition of strain B26 to wild type and to icdh mutant line led to a slight induction but not biologically significant relative to their respective controls. Thus, B26 has no effect on the expression of the ICDH gene, both in the wild type and the mutant backgrounds. Our results indicate that root exudates and individual organic acids play an important role in selective recruitment and colonization of PGPR and inducing biofilm. The current study increases the understanding of molecular mechanisms behind biofilm induction by organic acids.

Effects of root endophytic fungus, Microdochium bolleyi on cadmium uptake, translocation and tolerance by Hordeum vulgare L.

Endophytic fungi can have a positive impact on phytoremediation of heavy metals, but the effects of endophytic fungus Microdochium bolleyi on extraction of Cd by barley, have not been previously examined. Therefore, the objective of the present study was to assess the effects of M. bolleyi (strain B26) on cadmium (Cd) tolerance, accumulation and translocation by barley (Hordeum vulgare L.) (Sararood cultivar) under Cd stress. Barley plants were inoculated with B26 in Cd-added sands (0, 10, 30, 60 mg Cd kg−1 sand), and the various attributes of growth along with the amount of Cd in barley were investigated after two months. The results indicated that fungal inoculation significantly improved (p < 0.05) plant growth in the presence of Cd by enhancing factors of plant growth; shoot length increased by 8.93%, 11.61% and 5.59%, root length by 26.47%, 12.39% and 13.95%, dry root biomass by 6.35%, 8.57% and 28.57%, dry shoot biomass by 11.39%, 8.25% and 4.81% in soil containing 10, 30 and 60 mg Cd kg−1, respectively. The increases in chlorophyll content were 16.74% and 9.97% under 10 and 30 mg Cd kg−1 treatments, in turn. In terms of Cd accumulation, fungal inoculation increased the amount of Cd in the barley roots, by 44%, 27.95% and 25.18% in soil containing 10, 30 and 60 mg Cd kg−1, respectively, but it remained the same in plant leaves whether the plants were inoculated or not. The results suggested B26 can be exploited to improve the potential of barley for the remediation of Cd contaminated sites.

Screening an Established Natural Product Library Identifies Secondary Metabolites That Potentiate Conventional Antibiotics.

Health organizations worldwide have warned that we are on the cusp of a "post-antibiotic era," necessitating new approaches to combat antibiotic resistant infections. One such approach is the development of antibiotic adjuvants, which have little or no inherent antibiotic activity at their active concentrations but instead potentiate the activity of antibiotics against antibiotic-resistant bacteria. Recently, we demonstrated that meridianin D, a natural product originally reported to have activity against Staphylococcus aureus and Mycobacterium tuberculosis, possesses the ability to reverse colistin resistance in colistin resistant bacteria. As most natural product screens typically involve screening for only certain activities (anticancer, antiviral, and antimicrobial are typical), we posited that the meridianin D discovery was not unique and there are potentially many natural products that have adjuvant activity. To explore this, the National Cancer Institute (NCI) Natural Product Library Set IV was screened for adjuvant activity using four classes of antibiotics (β-lactams, aminoglycosides, macrolides, and polymyxins) against three bacterial pathogens (methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumannii, and Klebsiella pneumoniae). Sixteen compounds suppressed β-lactam resistance in MRSA, five of which effected a 16-fold reduction in the oxacillin minimum inhibitory concentration (MIC). Two natural products effectively suppressed aminoglycoside resistance in both of the Gram-negative species tested, and no hits were observed with macrolides. In contrast, a larger number of natural product adjuvants were identified when screening against colistin-resistant strains of A.baumannii and K.pneumoniae. Nine compounds reduced the colistin MIC to its breakpoint or lower (up to a 1024-fold reduction). Clorobiocin, novobiocin, and prodigiosin were most effective, reducing the colistin MIC in K.pneumoniae strain B9 to 2 μg/mL at concentrations as low as 0.625, 2.5, and 1.25 μM, respectively. Restored sensitivity to colistin with these compounds does not appear to coincide with known mechanisms of colistin resistance.

Phylogenetic characterization and screening of halophilic bacteria from Algerian salt lake for the production of biosurfactant and enzymes

Environments containing significant concentration of NaCl such as salt lakes harbor extremophiles microorganisms which have a great biotechnology interest. To explore the diversity of Bacteria in Chott Tinsilt (Algeria), an isolation program was performed. Water samples were collected from the saltern during the pre-salt harvesting phase. This Chott is high in salt (22.47% (w/v). Seven halophiles Bacteria were selected for further characterization. The isolated strains were able to grow optimally in media with 10–25% (w/v) total salts. Molecular identification of the isolates was performed by sequencing the 16S rRNA gene. It showed that these cultured isolates included members belonging to the Halomonas, Staphylococcus, Salinivibrio, Planococcus and Halobacillus genera with less than 98% of similarity with their closest phylogenetic relative. The halophilic bacterial isolates were also characterized for the production of biosurfactant and industrially important enzymes. Most isolates produced hydrolases and biosurfactants at high salt concentration. In fact, this is the first report on bacterial strains (A4 and B4) which were a good biosurfactant and coagulase producer at 20% and 25% ((w/v)) NaCl. In addition, the biosurfactant produced by the strain B4 at high salinity (25%) was also stable at high temperature (30-100°C) and high alkalinity (pH 11).

Production of antifungal metabolites by the antagonistic bacterial isolate Pseudomonas resinovorans B11

The production of antifungal compound(s) by an indigenous Pseudomonas resinovorans strain B11, showing antagonistic activity against Monosporascus cannonballus, the causal fungus of muskmelon Monosporascus root rot and vine decline disease was studied. The crude antibiotics were extracted from the cell-free culture filtrate of P. resinovorans B11 by solvent extraction. Analysis of the antibiotics preparation by thin layer chromatography revealed a prominent band with an Rf of 0.23 under ultraviolet light. Results of the gas chromatography–mass spectrometry analysis revealed that two compounds with retention time (RT) of 4.25 min and 10.58 min were present in the fluorescent band eluted at Rf 0.23. By comparing the mass spectra of these compounds with those found in the NIST/ Wiley database, these compounds were identified as 5-hydroxy-2-pentanone (RT: 4.25 min) and 4-hydroxy-4-methyl-2-pentanone (RT: 10.58 min) with molecular weights of 102.13 and 116.16, respectively. The compound 4-hydroxy-4-methyl-2-pentanone has been described as one of the components of antibiotics produced by other soil bacteria. However, this is the first report of production of 4-hydroxy-4-methyl-2-pentanone by P. resinovorans B11.

An Effective Degumming Technology for Ramie Fibers Based on Microbial Coculture Strategy

ABSTRACT Microbial treatment of natural fibers is a preferred alternatives in ramie degumming process as compared to conventional chemical degumming technology with alkaline treatment at high temperature. Usually, it is difficult to degrade the noncellulosic components of ramie bast completely with a single strain in the mono-culturing degumming system. Microbial coculture strategy has been widely used in biotechnology, especially in the degradation of biological materials. In the present study, five strains for ramie degumming were identified as Dickeya dadantii strain DCE-01, Bacillus subtilis strain 1101, Bacillus sp. B6, Bacillus cereus strain B7, and Bacillus cereus strain B8 by sequencing of 16 S rRNA genes. Enzymatic activities characterization, ramie degumming experiments with mono-culturing systems, and the evaluation of strain compatibility showed that group DCE-01/B7 were the most suitable pairs for the construction of bacterial coculturing system. After preliminary optimization of coculturing fermentation condition, the weight loss weight ratio of ramie fibers was 27%, which was increased 13.6% and 8.9% while compared to mono-culturing systems of strain B7 and DCE-01 respectively. These data highlighted the benefit of microbial coculture strategy in the application of ramie degumming process, and indicated a higher-efficiency alternative for the microbial degumming in the textile industry.

Beauveria bassiana for the control of leafcutter ants: strain and host differences

ABSTRACT Leafcutter ants are a serious pest for forestry plantations and crops in Latin America. They have been traditionally controlled using chemical synthetic pesticides, which are known to have many negative effects to non-target organisms and the environment. Therefore, there is an urgent need for the development of alternative strategies of control, among which the biological control using fungal pathogens is a promising one. We evaluated in laboratory 3 strains of Beauveria bassiana (B5, B6, B7) against workers from 4 to 7 field colonies from 5 species of Acromyrmex leafcutter ant species which are considered pests in the region. Our results showed that all strains were pathogenic, although there are some ant species that turned out to be more susceptible either due to their intrinsic immunity or the natural load of pathogens they carried. The three strains were similarly effective for 3 of the 5 species, A. ambiguus, A. crassispinus, and A. lundii, being responsible for more than 80% of their mortality overriding the effect of their natural pathogens. Only strain B6 was able to kill a similar percentage of ants of A. heyeri, and strain B7 half of them. B5 in A. heyeri, as well as all three strains in A. lobicornis, were responsible for up to 30% of the mortality, but with the additive effect of the pathogens naturally brought by these ants accounted for a 70% of their mortality. We recommend using B6 to test the control of Acromyrmex leaf-cutting ants in the field.