Bacillus Methylotrophicus Research Articles

Exploring the impact of plant growth-promoting bacteria in alleviating stress on Aptenia cordifolia subjected to irrigation with recycled water in multifunctional external green walls

BackgroundRapid urbanization and population growth exert a substantial impact on the accessibility of drinking water resources, underscoring the imperative for wastewater treatment and the reuse of non-potable water in agriculture. In this context, green walls emerge as a potential solution to augment the purification of unconventional waters, simultaneously contributing to the aesthetic appeal and enjoyment of urban areas. This study aims to optimize water management in green walls by investigating the impact of bacterial strains on the biochemical properties and performance of the ornamental accumulator plant, Aptenia cordifolia, grown with various unconventional water sources. The experiments were designed as split plots based on a completely randomized block design with three replications. The main factor was recycled water with three levels (gray water, wastewater from the Kashfroud region of Mashhad, and urban water (control)). The sub-factor included different bacterial strains at four levels, composed of various bacteria combinations, (B1: Psedoumonas flucrecens + Azosporillum liposferum + Thiobacillus thioparus + Aztobactor chorococcum, B2: Paenibacillus polymyxa + Pseudomonas fildensis + Bacillus subtilis + Achromobacter xylosoxidans + Bacillus licheniform, B3: Pseudomonas putida + Acidithiobacillus ferrooxidans + Bacillus velezensis + Bacillus subtilis + Bacillus methylotrophicus + Mcrobacterium testaceum, and the control level without bacterial application (B0).ResultThe findings revealed significant differences at the 5% probability level across all morphophysiological traits, including plant height, the number and length of lateral branches, growth index, and plant coverage. Moreover, superior morphophysiological traits were observed in plants cultivated in substrates inoculated with wastewater irrigation. Substrates inoculated with bacteria exhibited the highest relative water content (RWC) and chlorophyll levels, coupled with the lowest relative saturation deficit (RSD), electrolyte leakage (EL), and carotenoid levels. Furthermore, plant growth-promoting bacteria (PGPB), from a biochemical perspective, were associated with increased carbohydrates, total protein, and anthocyanin. They also contributed to controlling oxidative stress caused by free radicals by enhancing the activity of antioxidant enzymes, such as guaiacol peroxidase (GPX), polyphenol oxidase (PPO), ascorbate peroxidase (APX), and peroxidase (POD), while reducing catalase enzyme (CAT) activity. This led to increased resistance to stress, as evidenced by a decrease in malondialdehyde and proline levels. The study concludes that the MIX B3, being both ecofriendly and economical, represents an effective strategy for mitigating the adverse effects of wastewater on plants.ConclusionThis study showed that plant irrigation using wastewater increases the levels of proline, phenols and oxidative stress. However, the application of plant growth promoting bacteria (PGPB) reduced oxidative damage by increasing antioxidant activity and decreasing proline and phenol levels. These findings show the potential of bacterial treatments to improve plant growth and reduce adverse effects of recycled water irrigation.

BmfR, a novel GntR family regulator, regulates biofilm formation in marine-derived, Bacillus methylotrophicus B-9987

Biofilms are common living states for microorganisms, allowing them to adapt to environmental changes. Numerous Bacillus strains can form complex biofilms that play crucial roles in biocontrol processes. However, our current understanding of the molecular mechanisms of biofilm formation in Bacillus is mainly based on studies of Bacillus subtilis. Knowledge regarding the biofilm formation of other Bacillus species remains limited. In this study, we identified a novel transcriptional regulator, BmfR, belonging to the GntR family, that regulates biofilm formation in marine-derived Bacillus methylotrophicus B-9987. We demonstrated that BmfR induces biofilm formation by activating the extracellular polysaccharide structural genes epsA-O and negatively regulating the matrix gene repressor, SinR; of note it positively affects the expression of the master regulator of sporulation, Spo0A. Furthermore, database mining for BmfR homologs has revealed their widespread distribution among many bacterial species, mainly Firmicutes and Proteobacteria. This study advances our understanding of the biofilm regulatory network of Bacillus strains, and provides a new target for exploiting and manipulating biofilm formation.

Mechanisms of Cell Wall Degrading Enzymes from Bacillus methylotrophicus and Bacillus subtilis in Suppressing Foliar Blight Pathogens

Bacillus strains are potent Biocontrol agents (BCAs) and have been identified as an effective way to control the growth of phytopathogens of wheat. Through a direct inhibition mechanism which involves the production of cell wall degrading enzymes (proteases, glucanase, and chitinases) and siderophores they suppress the foliar blight disease. Both the strains of Bacillus P10 and UP11 shows growth inhibition Alternaria triticina (77.56%, 67.83%) and Bipolaris sorokiniana (73.97%, 62.16%) through a dual culture assay. These strains were subsequently examined for their ability to produce cell wall-degrading enzymes i.e., chitinase, protease, and β-1,3-glucanases and antifungal metabolites i.e., siderophores. It was found that when the antagonist’s bacteria were Co-cultured with fungal pathogens then maximum production of hydrolytic enzymes and siderophore was achieved at 96 hrs, but when both strains P10 and UP11 were alone maximum production was found at 48 hrs i.e., the exponential phase. The current study determined that Bacillus methylotrophicus (P10) and Bacillus subtilis (UP11) are highly effective strain for controlling Foliar Blight disease. Direct or Antibiosis is the main mechanism involved in this study. Further research on the interaction mechanisms between Bacillus-derived compounds and host plants is necessary.

Biocontrol agent amendments shape the soybean rhizosphere in a cyst nematode (Heterodera glycines) conducive soil over a two-year field trial

Plant-associated beneficial microorganisms play a vital role in promoting plant health, fitness, and disease suppression, leading to improved plant growth and protection against specific plant parasites. Microbial amendments may reduce nematode parasite populations and ensure plant yield, yet their long-term impact on the native plant microbiome under field conditions is not well understood. In this study, we evaluated the effectiveness of biocontrol products against soybean cyst nematode (SCN) using two application methods over a two-year period under field conditions. Pochonia chlamydosporia PC10 (Rizotec), Bacillus methylotrophicus UFPEDA 20 (Onix), and Trichoderma koningiopsis GF 362 were applied either through seed inoculation or in-furrow treatment at planting. The treatments effectively reduced the nematode population, with T. koningiopsis showing significant deviations from the control and leading to a notable increase in yield. No difference in the Shannon diversity index was detected for the alpha-diversity of root-associated 16S, ITS2, and 18S communities. The dominant phyla were Proteobacteria, Acidobacteria, Actinobacteria for 16S; Ascomycota, Basidiomycota, Mortierellomycota for ITS2; and Ascomycota, and Cercozoa for 18S. In the 16S community, T. koningiopsis and B. methylotrophicus caused a 25 % increase in the relative abundance of Sphingomonas spp. compared to the control. Additionally, the relative abundance of Mortierella spp. significantly increased by 50 % in both the T. koningiopsis and B. methylotrophicus treatments compared to the control. Both treatments also led to a significant reduction in Fusarium spp. by 37.5 % and 31.5 %, respectively. Co-occurrence network analysis revealed that communities were disrupted after the first application, but grew more intricate and cohesive after the second year of biocontrol product amendment. T. koningiopsis and B. methylotrophicus demonstrated potential in reducing nematode and Fusarium populations, leading to increased yield production. However, under high nematode pressure, relying solely on biocontrol measures does not guarantee a reduction in SCN population or yield improvement. Manipulating the microbial community to reduce harmful organisms and promote biocontrol-related species may offer long-term benefits.

Immune protection of grass carp by oral vaccination with recombinant Bacillus methylotrophicus expressing the heterologous tolC gene

In the field of aquaculture, the enhancement of animal health and disease prevention is progressively being tackled using alternatives to antibiotics, including vaccines and probiotics. This study was designed to evaluate the potential of a recombinant Bacillus methylotrophicus, engineered to express the outer membrane channel protein TolC of Aeromonas hydrophila AH3 and the green fluorescent protein GFP, as an oral vaccine. Initially, the genes encoding tolC and GFP were cloned into a prokaryotic expression system, and anti-TolC mouse antiserum was generated. Subsequently, the tolC gene was subcloned into a modified pMDGFP plasmid, which was transformed into B. methylotrophicus WM-1 for protein expression. The recombinant B. methylotrophicus BmT was then administered to grass carp via co-feeding, and its efficacy as an oral vaccine was assessed. Our findings demonstrated successful expression of the 55 kDa TolC and 28 kDa GFP proteins, and the preparation of polyclonal antibodies with high specificity. The BmT exhibited stable expression of the GFP-TolC fusion protein and excellent genetic stability. Following oral immunization, significant elevations were observed in serum-specific IgM levels and the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), and lysozyme (LZM) in grass carp. Concurrently, significant upregulation of immune-related genes, including IFN-I, IL-10, IL-1β, TNF-α, and IgT, was noted in the intestines, head kidney, and spleen of the grass carp. Colonization tests further revealed that the BmT persisted in the gut of immunized fish even after a fasting period of 7 days. Notably, oral administration of BmT enhanced the survival rate of grass carp following A. hydrophila infection. These results suggest that the oral BmT vaccine developed in this study holds promise for future applications in aquaculture.

Molecular characterization of apple endophytic bacteria and biological effect on Alternaria rot on apple

AbstractApple rot disease, caused by Alternaria alternata, is causing significant losses in apple production, especially in post‐harvest periods. Alternaria alternata, was isolated from rotten apple fruit of cv Amasya. Identification of the strain isolated from rotten apple fruit was made by ITS sequence and morphological analysis. In the present study, 58 different endophytic bacteria strains were isolated from apple fruit for use in apple rot disease control. Among the isolated strains, 26 endophyte strains were determined to inhibit the radial growth of mycelia of A. alternata in binary culture in PDA media. Based on 16S rRNA sequencing analysis, these antagonistic endophytic bacteria strains were identified as Bacillus ssp. Bacillus methylotrophicus (ib17) showed the highest significant inhibitory effect on the mycelial growth of A. alternata at a rate of 79.5% in PDA medium. The results of in vivo experiments showed that Bacillus licheniformis (ib20) achieved 100% biocontrol when endophyte bacterial strains were inoculated 24 h before the inoculation of A. alternata. When the three bacteria species and A. alternata were inoculated simultaneously, Bacillus myloliquefaciens (ib1), Bacillus licheniformis (ib21) and the Endophytic bacterium (ib16) showed the highest biocontrol efficacy against A. alternata at 81.8%. Furthermore, when the bacterial strains were inoculated at 24 h after inoculation of A. alternata, B. licheniformis (ib21) showed the highest biocontrol efficacy of 83.3% against the fungal pathogen compared to the controls. The endophytic bacterial strains produced fungal cell wall hydrolysing enzymes such as chitinase, cellulase, amylase and protease. According to the results of this study, apple endophytic bacteria are potential candidates to control apple decay caused by A. alternata through cell wall hydrolysing enzymes and reduce disease severity. However, the efficacy of the biological control was dependent on the applied time of epiphytic bacterial strains. Further research is needed on the biochemical mechanisms underlying the activity of these bacteria against A. alternata.

Bacillus methylotrophicus DCS1: Production of Different Lipopeptide Families, In Vitro Antifungal Activity and Suppression of Fusarium Wilt in Tomato Plants.

The present work aims to quantitatively and qualitatively monitor the production of lipopeptide mixtures by Bacillus methylotrophicus DCS1 strain in Landy medium and to investigate the antifungal activities of DCS1 strain and its produced lipopeptides. The in vitro activities were tested by the direct confrontation and agar well diffusion methods, while the in vivo study was carried out in order to test the efficiency of DCS1 bacterial suspension in the control of Fusarium wilt in tomato plants. Identification of lipopeptides by mass spectrometry (LC/MSD-TOF) showed that lipopeptide isoforms produced during the first 24h and 48h of fermentation are identical, belonging to bacillomycin D and fengycins A and B homologues with a difference in the yield of production. After 72h of fermentation corresponding to the end of incubation period, B. methylotrophicus DCS1 is able to produce a mixture of surfactin, pumilacidin, iturin A/mycosubtilin, iturin C1, bacillomycin D and fengycins A and B isoforms. The results of in vitro antifungal experiments suggest that B. methylotrophicus DCS1 has a significant potential as a biocontrol agent, owing to lipopeptides produced, endowed with antifungal activity against several phytopathogenic fungi. The curative treatment of tomato plants with DCS1 bacterial suspension was more effective in the protection against Fusarium oxysporum f. sp. radicis-lycopersici (FORL) than the preventive treatment by comparing the average number of leaves remaining healthy after 30days of each treatment and the appearance of tomato plants roots. The results indicate that B. methylotrophicus DCS1 exhibit a significant suppression of Fusarium wilt symptoms in tomato plants comparable to that of commercial fungicides and could be an alternative to chemically synthesized pesticides.

Control of Meloidogyne javanica in banana by endophytic bacteria

Abstract The aim of this work was to evaluate the effect of 40 endophytic bacteria isolates on the control of Meloidogyne javanica in ‘Prata-Anã’ banana seedlings. Two experiments were carried out in a completely randomized design with eight replicates. In each trial, 20 bacteria isolates and control were evaluated. Bacterial suspensions were applied to substrates during the acclimatization of seedlings at 15 and 30 days. On the 31st day, seedlings were transplanted into pots and soil was infested with M. javanica egg suspension at 8 days. After 90 days, the following variables were evaluated: number of galls, egg masses, eggs per root, reproduction factor (RF), second-stage juveniles, and shoot dry matter. The results of nematological variables were submitted to Principal Components Analysis. In trial I, the variables that most contributed to data variability were as follows: number of eggs and RF. In trial II, RF had greater influence. Of the 40 isolates evaluated, 39 reduced RF, and of the 20 isolates evaluated in the first trial, all reduced the number of eggs per root. Bacillus methylotrophicus EB26, Bacillus cereus EB25, and Bacillus sp. EB37 isolates stood out in the control of nematodes, with RF reduction above 80%.

Decomposed chicken feather: A biostimulant to lettuce (Lactuca sativa) growth

It is crucial to produce plant growth biostimulants from waste and renewable resources. A study was carried during 2020 at the Soil and Water Research Institute, Karaj, Iran to evaluate the effect of decomposed chicken feather as a biostimulant on lettuce (Lactuca sativa L.) growth. A total of 29 soil samples from 15 Iranian regions were used to isolate and identify the bacteria and 31 strains that were able to produce keratinase and capable of feather degrading were isolated. Then, 8 isolates that were able to degrade the feather during 7 days were selected as the superior strains. Based on the results Bacillus siamensis c11, Bacillus methylotrophicus gh1 and Bacillus methylotrophicus a2 were identified as the new strains that can produce keratinase enzyme. Then, the effect of foliar spraying of the solutions produced from feather degradation by the new strains (c11, gh1, and a2) on the growth of lettuce was investigated. The results showed that the solution produced by methylotrophicus gh1 strain significantly increased the fresh and dry weight of the shoot and root (respectively, 25.9, 36.9, 34.1 and 51.9% increase compared to the control). It is concluded that the microbial solution of these three microbes as a consortium could be quite a new addition on one hand, could also reduce the human allergy as a via- medium of waste disposal.

Co-production of lipases and biosurfactants by Bacillus methylotrophicus in solid-state fermentation.

The online version contains supplementary material available at 10.1007/s13205-023-03910-7.

Long-term benefit contribution of chemical and biological nematicide in coffee nematode management in soil microbial diversity and crop yield perspectives

The plant-parasitic root-knot nematode Meloidogyne exigua causes significant damage and is an important threat in Coffea arabica plantations. The utilization of plant-beneficial microbes as biological control agents against sedentary endoparasitic nematodes has been a longstanding strategy. However, their application in field conditions to control root-knot nematodes and their interaction with the rhizospheric microbiota of coffee plants remain largely unexplored. This study aimed to investigate the effects of biological control agent-based bioproducts and a chemical nematicide, used in various combinations, on the control of root-knot nematodes and the profiling of the coffee plant rhizomicrobiome in a field trial. The commercially available biological products, including Trichoderma asperellum URM 5911 (Quality), Bacillus subtilis UFPEDA 764 (Rizos), Bacillus methylotrophicus UFPEDA 20 (Onix), and nematicide Cadusafos (Rugby), were applied to adult coffee plants. The population of second-stage juveniles (J2) and eggs, as well as plant yield, were evaluated over three consecutive years. However, no significant differences were observed between the control group and the groups treated with bioproducts and the nematicide. Furthermore, the diversity and community composition of bacteria, fungi, and eukaryotes in the rhizosphere soil of bioproduct-treated plants were evaluated. The dominant phyla identified in the 16 S, ITS2, and 18 S communities included Proteobacteria, Acidobacteria, Actinobacteria, Ascomycota, Mortierellomycota, and Cercozoa in both consecutive years. There were no significant differences detected in the Shannon diversity of 16 S, ITS2, and 18 S communities between the years of data. The application of a combination of T. asperellum, B. subtilis, and B. methylotrophicus, as well as the use of Cadusafos alone and in combination with T. asperellum, B. subtilis, and B. methylotrophicus, resulted in a significant reduction (26.08%, 39.13%, and 21.73%, respectively) in the relative abundance of Fusarium spp. Moreover, the relative abundance of Trichoderma spp. significantly increased by 500%, 200%, and 100% at the genus level, respectively, compared to the control treatment. By constructing a co-occurrence network, we discovered a complex network structure among the species in all the bioproduct-treated groups. However, our findings indicate that the introduction of exogenous beneficial microbes into field conditions was unable to modulate the existing microbiota significantly. These findings suggest that the applied bioproducts had no significant impact on the reshaping of the overall microbial diversity in the rhizosphere microbiome but rather recruited selected microrganisms and assured net return to the grower. The results underscore the intricate nature of the rhizosphere microbiome and suggest the necessity for alternate biocontrol strategies and a re-evaluation of agricultural practices to improve nematode control by aligning with the complex ecological interactions in the rhizosphere.

Enhanced poly-γ-glutamic acid synthesis in Corynebacterium glutamicum by reconstituting PgsBCA complex and fermentation optimization

Previously, a novel Corynebacterium glutamicum strain for the de novo biosynthesis of tailored poly-γ-glutamic acid (γ-PGA) has been constructed by our group. The strain was based on the γ-PGA synthetase complex, PgsBCA, which is the only polyprotein complex responsible for γ-PGA synthesis in Bacillus spp. In the present study, PgsBCA was reconstituted and overexpressed in C. glutamicum to further enhance γ-PGA synthesis. First, we confirmed that all the components (PgsB, PgsC, and PgsA) of γ-PGA synthetase derived from B. licheniformis are necessary for γ-PGA synthesis, and γ-PGA was detected only when PgsB, PgsC, and PgsA were expressed in combination in C. glutamicum. Next, the expression level of each pgsB, pgsC, and pgsA was tuned in order to explore the effect of expression of each of the γ-PGA synthetase subunits on γ-PGA production. Results showed that increasing the transcription levels of pgsB or pgsC and maintaining a medium-level transcription level of pgsA led to 35.44% and 76.53% increase in γ-PGA yield (γ-PGA yield-to-biomass), respectively. Notably, the expression level of pgsC had the greatest influence (accounting for 68.24%) on γ-PGA synthesis, followed by pgsB. Next, genes encoding for PgsC from four different sources (Bacillus subtilis, Bacillus anthracis, Bacillus methylotrophicus, and Bacillus amyloliquefaciens) were tested in order to identify the influence of PgsC-encoding orthologues on γ-PGA production, but results showed that in all cases the synthesis of γ-PGA was significantly inhibited. Similarly, we also explored the influence of gene orthologues encoding for PgsB on γ-PGA production, and found that the titer increased to 17.14 ± 0.62 g/L from 8.24 ± 0.10 g/L when PgsB derived from B. methylotrophicus replaced PgsB alone in PgsBCA from B. licheniformis. The resulting strain was chosen for further optimization, and we achieved a γ-PGA titer of 38.26 g/L in a 5 L fermentor by optimizing dissolved oxygen level. Subsequently, by supplementing glucose, γ-PGA titer increased to 50.2 g/L at 48 h. To the best of our knowledge, this study achieved the highest titer for de novo production of γ-PGA from glucose, without addition of L-glutamic acid, resulting in a novel strategy for enhancing γ-PGA production.

Combined application of microbial inoculant and kelp-soaking wastewater promotes wheat seedlings growth and improves structural diversity of rhizosphere microbial community

Industrial processing of kelp generates large amounts of kelp-soaking wastewater (KSW), which contains a large amount of nutrient-containing substances. The plant growth-promoting effect might be further improved by combined application of growth-promoting bacteria and the nutrient-containing KSW. Here, a greenhouse experiment was conducted to determine the effect of the mixture of KSW and Bacillus methylotrophicus M4-1 (MS) vs. KSW alone (SE) on wheat seedlings, soil properties and the microbial community structure in wheat rhizosphere soil. The available potassium, available nitrogen, organic matter content and urease activity of MS soil as well as the available potassium of the SE soil were significantly different (p < 0.05) from those of the CK with water only added, increased by 39.51%, 36.25%, 41.61%, 80.56% and 32.99%, respectively. The dry and fresh weight of wheat seedlings from MS plants increased by 166.17% and 50.62%, respectively, while plant height increased by 16.99%, compared with CK. Moreover, the abundance and diversity of fungi in the wheat rhizosphere soil were significantly increased (p < 0.05), the relative abundance of Ascomycetes and Fusarium spp. decreased, while the relative abundance of Bacillus and Mortierella increased. Collectively, the combination of KSW and the plant growth-promoting strain M4-1 can promote wheat seedlings growth and improve the microecology of rhizosphere microorganisms, thereby solving the problems of resource waste and environmental pollution, ultimately turning waste into economic gain.

The application of plant growth-promoting rhizobacteria enhances the tolerance of tobacco seedling to salt stress

The application of plant growth-promoting rhizobacteria (PGPR) is a novel and an efficient strategy for improving soil degradation and productivity. However, the effect of PGPR on tobacco (Nicotiana tabacum L.) seedling growth under salt stress remains unclear. Here, microcosm experiments were designed to verify the effects of Bacillus cereus TC012 (BC), Bacillus methylotrophicus TC023 (BM), and Bacillus amyloliquefacien TC037 (BA) on tobacco grown in salt-affected soil. The results showed that BC, BM, and BA treatments significantly increased the height of tobacco plants by 38.65%, 91.94%, and 90.66%, respectively. Furthermore, the growth of various components of tobacco plant, such as stem girth, seedling biomass, carotenoid, and chlorophyll were stimulated in salt-affected soils. The changes in the salinity of the tobacco plant mostly relies on the improvement of proline, soluble protein, soluble sugar content, plant protective enzymatic activity, and K+/Na+ ratios. Increases in indole-3-acetic acid, zeatin riboside and gibberellic acid also promoted tobacco growth. Additionally, inoculation with PGPR enhanced the enzymatic activity of laccase, urease, neutral protease, acid phosphatase, and sucrase in soil samples and had positive effects on the physicochemical properties. The soil bacterial communities significantly improved after inoculation with PGPR. In particular, the relative abundance of Pseudomonas and Bacillus significantly increased. Overall, PGPR inoculation has great potential to alleviate salt damage in tobacco plants and may have far reaching benefits to the agricultural community.

Biocontrol Efficacy of Bacillus methylotrophicus TA-1 Against Meloidogyne incognita in Tomato.

Root-knot nematodes (RKNs) are harmful plant-parasitic nematodes of tomatoes which can cause significant yield losses. Therefore, there is increasing interest in exploring the application of bacterial nematicides. The bacterium Bacillus methylotrophicus TA-1 is a broad-spectrum biological control agent; however, its effect on RKNs control remains largely unclear. In this study, the toxicity of B. methylotrophicus TA-1 against Meloidogyne incognita was investigated in vitro, and the potential of B. methylotrophicus TA-1 to decrease infection of RKNs in tomato were evaluated in pot and field trials. Results showed that B. methylotrophicus TA-1 exhibited high nematicidal activity against second-stage juveniles (J2s) and eggs of M. incognita with 50% lethal concentration (LC50) values of 5.80 and 7.00 × 108 colony forming units (CFU)/ml, respectively. In the pot experiments and field trials conducted in 2020 and 2021, tomato plants treated with B. methylotrophicus TA-1 soil drench applied once at 3, 6, and 9 × 108 CFU/plant had significantly higher plant height and greater yield compared with the untreated control. Tomato yields of the treated plots with B. methylotrophicus TA-1 in 2 consecutive years' field trials were between 53.4 to 66.1 and 52.8 to 61.5 t/ha, while they were 49.7 and 48.2 t/ha in the untreated control for each year, respectively. The lowest population densities of M. incognita at 30 and 60 days after treatment were 119 and 135 J2s per 100 g soil in 2020 and 43 and 118 J2s in 2021 in TA-1-treated plots. The lowest gall index of 4.7 and 3.3 in 2020 and 2021, respectively, and the highest yield were all observed in the TA-1 at 9 × 108 CFU/plant treated plants, with no significant differences with the commercial control abamectin. These results provided a basis for further studies of B. methylotrophicus TA-1 formulations, application doses, frequencies, and mechanisms of action, which are necessary before it could be used as a component of integrated management programs to manage RKNs in tomato production.

Bioelectrogeneic performance of air-cathode microbial fuel cells with diesel contaminants

Bioremediation of diesel contaminants and then harnessing the bioenergy could be another cost‐effective and eco‐friendly solution to hydrocarbons soil contaminants. Four series of parallel circuit air–cathode MFCs (100 mL working volume) were operated under different diesel concentrations using acclimated bacterial consortium from diesel contaminated soil. Maximum current (Imax = 43.11 mA) under applied potential was recorded using fuel cell (DMFC-31DMFC-3 = 50mlL−1 diesel concentration in microbial fuel cells.1) fed with 50 mlL−1 diesel (substrate), whereas it was 10 mA in DMFC-122DMFC-1 = 0mlL−1 diesel concentration in microbial fuel cells. (0 mlL−1), Imax of 9.6 mA in DMFC-23DMFC-2 = 10mlL−1 diesel concentration in microbial fuel cells.3(10 mlL−1) while in DMFC-444DMFC-4 = 100mlL−1 diesel concentration in microbial fuel cells. (100 mlL−1) Imax of 18.47 mA was recorded. Cyclic voltammogram and CLSM clearly indicated the effect of different diesel concentrations on the electrogenic performance of anode respiring bacteria (ARB). Six less explored, culturable species of ARB enriched bacteria on anodic biofilms in DMFC-3 were procured and characterized on molecular basis (16S rRNA gene) as Paenibacillus sp. (MN173851), Bacillus toyonensis (MN173853), Ochrobactrum sp. (MN173857), Bacillus sp. (MN173854), Bacillus methylotrophicus (MN173856), and Bacillus licheniformis (MN173855). Bioelectrochemical activity of Bacillus toyonensis (MN173853) was typically monitored for the first time in MFC reactors. Among the tested organisms, Bacillus sp., was found to have greatest biodegradation capability with rate of 88% followed by Paenibacillus sp. 85%, Ochrobactrum sp. 79% by fast decolourization of redox indicator. The present study verified the presence and suitability of ARB under the influence of diesel in MFCs.

Bacillus methylotrophicus Could Improve the Tolerance and Recovery Ability of the Tomato to Low-Temperature Stress and Improve Fruit Quality

Low-temperature stress seriously affects the growth, development, yield, and quality of tomato production. Bacillus methylotrophicus is an important plant growth promoting rhizobacteria (PGPR). However, the role of B. methylotrophicus under low-temperature stress is poorly understood. Accordingly, the effects of B. methylotrophicus (‘VL-10′) on tomato cold stress (15 °C/8 °C, 12 h/12 h, and day/night) were studied. B. methyltrophicus ‘VL-10′ was added into the substrate at the time of sowing, and the plants were treated at a low temperature for 2 weeks after 40 days of growth. We found that the low temperature reduced the spatial distribution of the aboveground and underground sections of tomatoes and the leaf SPAD and photochemical efficiency of PS II (Fv/Fm). After low-temperature stress, the tomato flowering was delayed, the vitamin C and lycopene content in fruit decreased, and the nitrate content increased. However, inoculated with B. methyltrophicus ‘VL-10′ during sowing promoted the growth of tomato seedlings, enhanced the native defense ability of the tomatoes, and effectively reduced the cold shock response of the roots to cold damage and the adverse effects of low temperature on leaf SPAD and Fv/Fm. After the cultivation at normal temperature, the inoculat B. methyltrophicus ‘VL-10′ could rapidly regain plant growth levers, and eliminate the delay of low temperature on flowering. TOPSIS analysis showed that the nutritional quality of tomatoes could be effectively improved by inoculation with B. methyltrophicus ‘VL-10′ regardless of normal cultivation or low-temperature stress.

Potential Novel Plant Growth Promoting Rhizobacteria for Bio-Organic Fertilizer Production in the Oil Palm (Elaeis guineensis Jacq.) in Malaysia

The present study aimed to characterize the potential plant growth-promoting rhizobacteria (PGPR) based on biochemical tests based on eight bacterial isolates, and to identify potential PGPR based on the 16S rRNA sequencing molecular method. Eight potential PGPR strains (UPMC1166, UPMC1168, UPMC1254, UPMC1376, UPMC1389, UPMC1393, UPMC703 and UPMC704) isolated from the soils in the oil palm (Elaeis guineensis) estates across Malaysia were selected because of their most PGPR activities. They were screened for nitrogen fixation, phosphate and potassium solubilization, and production of indole-3-acetic acid (IAA). All isolates showed the ability to grow between pH 2 to 9 and survive from 2 to 15% (w/v) of the salt medium. Among the isolated PGPRs, four PGPRs (UPMC1166, UPMC1168, UPMC1254 and UPMC1389) showed the ability to fix nitrogen and had the potential to produce IAA. Furthermore, two PGPRs (UPMC1393 and UPMC1376) demonstrated the ability to solubilize phosphate, while three PGPRs (UPMC703, UPMC704, and UPMC1393) showed the ability to solubilize potassium. Therefore, all the above eight PGPR isolates can benefit the oil palm cultivation industry. The molecular identification based on 16S rRNA gene sequence revealed that UPMC1166 was identified as Bacillus methylotrophicus; UPMC1168 as B. siamensis; UPMC1254 as B. subtilis; UPMC1389 as B. albus; UPMC1376 as Lactobacillus plantarum; UPMC1393 as B. marisflavi; UPMC703 as Burkhoderiaanthina and UPMC704 as B. metallica. These novel strains can be further investigated for their viability and effectiveness for bio-organic fertilizer production and application in the immature stage of oil palm growth.

Effect of the bacterial community assembly process on the microbial remediation of petroleum hydrocarbon-contaminated soil.

The accumulation of petroleum hydrocarbons (PHs) in the soil can reduce soil porosity, hinder plant growth, and have a serious negative impact on soil ecology. Previously, we developed PH-degrading bacteria and discovered that the interaction between microorganisms may be more important in the degradation of PHs than the ability of exogenous-degrading bacteria. Nevertheless, the role of microbial ecological processes in the remediation process is frequently overlooked. This study established six different surfactant-enhanced microbial remediation treatments on PH-contaminated soil using a pot experiment. After 30 days, the PHs removal rate was calculated; the bacterial community assembly process was also determined using the R language program, and the assembly process and the PHs removal rate were correlated. The rhamnolipid-enhanced Bacillus methylotrophicus remediation achieved the highest PHs removal rate, and the bacterial community assembly process was impacted by deterministic factors, whereas the bacterial community assembly process in other treatments with low removal rates was affected by stochastic factors. When compared to the stochastic assembly process and the PHs removal rate, the deterministic assembly process and the PHs removal rate were found to have a significant positive correlation, indicating that the deterministic assembly process of bacterial communities may mediate the efficient removal of PHs. Therefore, this study recommends that when using microorganisms to remediate contaminated soil, care should be taken to avoid strong soil disturbance because directional regulation of bacterial ecological functions can also contribute to efficient removal of pollutants.

Enhanced lignocellulose degradation and composts fertility of cattle manure and wheat straw composting by Bacillus inoculation

Few studies on Bacillus inoculation have been reported for lignocellulose degradation and composts fertility during composting. This research explored the enhanced lignocellulose degradation and composts fertility of cattle manure and wheat straw composting by Bacillus inoculation. Bacillus methylotrophicus F-6, Bacillus velezensis T-B, and Bacillus haynesii R-1 were used in this research. The results indicated that Bacillus inoculation (1) prolonged the thermophilic phase by 1–2 days, (2) decreased the NH+4-N/NO-3-N value, E4/E6, and respiration activity for four days (RA4) of final composts, (3) increased the cellulose, hemicellulose, and lignin degradation rate by 17.1%− 46.4%, 16.9%− 34.5%, and 30.6%− 69.4%, and (4) increased biomass of plant growth by 8.6%− 42.5% (based on final dry matter) and 16.4%− 42.4% (based on final organic matter). Pearson correlation analysis indicated that total nitrogen, total phosphorous, total potassium, and relative abundance of Atopostipes, Proteiniphilum and Thermobifida of final compost were positively correlated to the plant growth. Bacillus is a genus of thermophilic bacteria that can improve microbial biodiversity and population, further altering the physical and chemical properties of compost. The results showed Bacillus inoculation is beneficial to improve compost maturity, promote lignocellulose degradation, and improve composts fertility.