Bacterial Lipopeptide Research Articles

Inhibitory activity of bacterial lipopeptides against Fusarium oxysporum f.sp. Strigae

This study investigated the influence of bacterial cyclic lipopeptides (LP; surfactins, iturins, fengycins) on microbial interactions. The objective was to investigate whether the presence of bacteria inhibits fungal growth and whether this inhibition is due to the release of bacterial metabolites, particularly LP. Selected endophytic bacterial strains with known plant-growth promoting potential were cultured in the presence of Fusarium oxysporum f.sp. strigae (Fos), which was applied as model fungal organism. The extracellular metabolome of tested bacteria, with a focus on LP, was characterized, and the inhibitory effect of bacterial LP on fungal growth was investigated. The results showed that Bacillus velezensis GB03 and FZB42, as well as B. subtilis BSn5 exhibited the strongest antagonism against Fos. Paraburkholderia phytofirmans PsJN, on the other hand, tended to have a slight, though non-significant growth promotion effect. Crude LP from strains GB03 and FZB42 had the strongest inhibitory effect on Fos, with a significant inhibition of spore germination and damage of the hyphal structure. Liquid chromatography tandem mass spectrometry revealed the production of several variants of iturin, fengycin, and surfactin LP families from strains GB03, FZB42, and BSn5, with varying intensity. Using plate cultures, bacillomycin D fractions were detected in higher abundance in strains GB03, FZB42, and BSn5 in the presence of Fos. Additionally, the presence of Fos in dual plate culture triggered an increase in bacillomycin D production from the Bacillus strains. The study demonstrated the potent antagonistic effect of certain Bacillus strains (i.e., GB03, FZB42, BSn5) on Fos development. Our findings emphasize the crucial role of microbial interactions in shaping the co-existence of microbial assemblages.

Granulocyte dynamics: a key player in the immune priming effects of crickets.

This study investigates immune priming effects associated with granulocytes in crickets through a comprehensive analysis. Kaplan-Meier survival analysis reveals a significant contrast in survival rates, with the heat-killed Bacillus thuringiensis (Bt)-primed group exhibiting an impressive ~80% survival rate compared to the PBS buffer-primed group with only ~10% survival 60 hours post live Bt infection. Hemocyte analysis underscores elevated hemocyte counts, particularly in granulocytes of the killed Bt-primed group, suggesting a correlation between the heat-killed Bt priming and heightened immune activation. Microscopy techniques further explore granulocyte morphology, unveiling distinctive immune responses in the killed Bt-primed group characterized by prolonged immune activation, heightened granulocyte activity, phagocytosis, and extracellular trap formation, contributing to enhanced survival rates. In particular, after 24 hours of injecting live Bt, most granulocytes in the PBS buffer-primed group exhibited extracellular DNA trap cell death (ETosis), while in the killed Bt-primed group, the majority of granulocytes were observed to maintain highly activated extracellular traps, sustaining the immune response. Gene expression analysis supports these findings, revealing differential regulation of immune-related genes such as antibacterial humoral response, detection of bacterial lipopeptides, and cellular response to bacteria lipopeptides. Additionally, the heat-killed Bt-primed group, the heat-killed E. coli-primed group, and the PBS-primed group were re-injected with live Bt 2 and 9 days post priming. Two days later, only the PBS-primed group displayed low survival rates. After injecting live Bt 9 days later, the heat-killed E. coli-primed group surprisingly showed a similarly low survival rate, while the heat-killed Bt-primed group exhibited a high survival rate of ~60% after 60 hours, with actively moving and healthy crickets. In conclusion, this research provides valuable insights into both short-term and long-term immune priming effects in crickets, contributing to our understanding of invertebrate immunity with potential applications in public health.

Diversification of Toll-like receptor 1 in swamp eel (Monopterus albus)

Toll-like receptor 1 (TLR1) is a pattern recognition receptor that plays critical roles in triggering immune activation via detecting bacterial lipoproteins and lipopeptides. In this study, the genetic characteristic of TLR1 was studied for an important aquaculture fish, swamp eel Monopterus albus. The eel has been seriously threatened by infectious diseases. However, a low level of genetic heterogeneity in the fish that has resulted from a demographic bottleneck presents further challenges in breeding for disease resistance. A comparison with the homologue of closely related species M. javanensis revealed that amino acid replacement (nonsynonymous) but not silent (synonymous) differences have accumulated nonrandomly over the coding sequences of the receptors at the early stage of their phylogenetic split. The combined results from comparative analyses of nonsynonymous-to-synonymous polymorphisms showed that the receptor has undergone significant diversification in M. albus driven by adaptive selection likely after the genetic bottleneck. Some of the changes reported here have taken place in the structures mediating heterodimerization with co-receptor TLR2, ligand recognition, and/or formation of active signaling complex with adaptor, which highlighted key structural elements and strategies of TLR1 in arms race against exogenous challenges. The findings of this study will add to the knowledge base of genetic engineering and breeding for disease resistance in the eel.

Bacterial Lipopeptides Are Effective against Pear Fire Blight.

Fire blight, a devastating disease caused by Erwinia amylovora, poses a significant threat to pear and apple trees in Xinjiang province, China. In an effort to combat this pathogen, we isolated 10 bacteria from various components of apple and crabapple trees and conducted screenings to assess their ability to inhibit E. amylovora in vitro. Through biochemical tests and partial 16S rRNA gene sequencing, we identified two promising strains, Priestia megaterium strain H1 and Bacillus subtilis strain I2. These strains were then evaluated for their efficacy in biocontrol under controlled laboratory conditions, focusing on immature fruits and leaves. Remarkably, all selected antagonists exhibited the capability to reduce the severity of the disease on both fruit and leaves. P. megaterium strain H1 and B. subtilis strain I2 exhibited significant reductions in disease incidence on both immature fruits and leaves compared to the control. Specifically, on immature fruits, they achieved reductions of 53.39% and 44.76%, respectively, while on leaves, they demonstrated reductions of 59.55% and 55.53%, respectively. Furthermore, during the study, we detected the presence of lipopeptides, including surfactin, iturins, bacillomycin D, and fengycins, in the methanol extract obtained from these two antagonistic bacteria using thin-layer chromatography (TLC). Based on the results obtained, B. subtilis strain I2 and P. megaterium strain H1 exhibit considerable potential for controlling fire blight. However, further evaluation of their efficacy under natural field conditions is essential to validate their practicality as a biocontrol method.

Dysregulated monocyte-derived macrophage response to Group B Streptococcus in newborns.

Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading pathogen of neonatal sepsis. The host-pathogen interactions underlying the progression to life-threatening infection in newborns are incompletely understood. Macrophages are first line in host defenses against GBS, contributing to the initiation, amplification, and termination of immune responses. The goal of this study was to compare the response of newborn and adult monocyte-derived macrophages (MDMs) to GBS. Monocytes from umbilical cord blood of healthy term newborns and from peripheral blood of healthy adult subjects were cultured with M-CSF to induce MDMs. M-CSF-MDMs, GM-CSF- and IFNγ-activated MDMs were exposed to GBS COH1, a reference strain for neonatal sepsis. GBS induced a greater release of IL-1β, IL-6, IL-10, IL-12p70 and IL-23 in newborn compared to adult MDMs, while IL-18, IL-21, IL-22, TNF, RANTES/CCL5, MCP-1/CCL2 and IL-8/CXCL8 were released at similar levels. MDM responses to GBS were strongly influenced by conditions of activation and were distinct from those to synthetic bacterial lipopeptides and lipopolysaccharides. Under similar conditions of opsonization, newborn MDMs phagocytosed and killed GBS as efficiently as adult MDMs. Altogether, the production of excessive levels of Th1- (IL-12p70), Th17-related (IL-1β, IL-6, IL-23) and anti-inflammatory (IL-10) cytokines is consistent with a dysregulated response to GBS in newborns. The high responsiveness of newborn MDMs may play a role in the progression of GBS infection in newborns, possibly contributing to the development of life-threatening organ dysfunction.

Gene expression of S100a8/a9 predicts Staphylococcus aureus-induced septic arthritis in mice.

Septic arthritis is the most aggressive joint disease associated with high morbidity and mortality. The interplay of the host immune system with the invading pathogens impacts the pathophysiology of septic arthritis. Early antibiotic treatment is crucial for a better prognosis to save the patients from severe bone damage and later joint dysfunction. To date, there are no specific predictive biomarkers for septic arthritis. Transcriptome sequencing analysis identified S100a8/a9 genes to be highly expressed in septic arthritis compared to non-septic arthritis at the early course of infection in an Staphylococcus aureus septic arthritis mouse model. Importantly, downregulation of S100a8/a9 mRNA expression at the early course of infection was noticed in mice infected with the S. aureus Sortase A/B mutant strain totally lacking arthritogenic capacity compared with the mice infected with parental S. aureus arthritogenic strain. The mice infected intra-articularly with the S. aureus arthritogenic strain significantly increased S100a8/a9 protein expression levels in joints over time. Intriguingly, the synthetic bacterial lipopeptide Pam2CSK4 was more potent than Pam3CSK4 in inducing S100a8/a9 release upon intra-articular injection of these lipopeptides into the mouse knee joints. Such an effect was dependent on the presence of monocytes/macrophages. In conclusion, S100a8/a9 gene expression may serve as a potential biomarker to predict septic arthritis, enabling the development of more effective treatment strategies.

Deciphering immune responses primed by a bacterial lipopeptide in wheat towards Zymoseptoria tritici.

Plant immunity induction with natural biocontrol compounds is a valuable and promising ecofriendly tool that fits with sustainable agriculture and healthy food. Despite the agroeconomic significance of wheat, the mechanisms underlying its induced defense responses remain obscure. We reveal here, using combined transcriptomic, metabolomic and cytologic approach, that the lipopeptide mycosubtilin from the beneficial bacterium Bacillus subtilis, protects wheat against Zymoseptoria tritici through a dual mode of action (direct and indirect) and that the indirect one relies mainly on the priming rather than on the elicitation of plant defense-related mechanisms. Indeed, the molecule primes the expression of 80 genes associated with sixteen functional groups during the early stages of infection, as well as the accumulation of several flavonoids during the period preceding the fungal switch to the necrotrophic phase. Moreover, genes involved in abscisic acid (ABA) biosynthesis and ABA-associated signaling pathways are regulated, suggesting a role of this phytohormone in the indirect activity of mycosubtilin. The priming-based bioactivity of mycosubtilin against a biotic stress could result from an interaction of the molecule with leaf cell plasma membranes that may mimic an abiotic stress stimulus in wheat leaves. This study provides new insights into induced immunity in wheat and opens new perspectives for the use of mycosubtilin as a biocontrol compound against Z. tritici.

Antifungal activities of Bacillus velezensis FJAT-52631 and its lipopeptides against anthracnose pathogen Colletotrichum acutatum.

This study was aim at investigating antifungal activities of Bacillus velezensis FJAT-52631 and its lipopeptides against Colletotrichum acutatum ex situ and in situ. The results showed that the strain FJAT-52631 and its crude lipopeptides (10 mg/ml) exhibited strong inhibitory effects on growth of C. acutatum FJAT-30256 with an inhibition rate of 75.3% and an inhibition zone diameter of 17.66 mm, respectively. Both the viable bacterial cultures and lipopeptides of FJAT-52631 could delay the onset of loquat anthracnose by 1 day and lower the incidence of loquat anthracnose in situ. The whole cultures of B. velezensis FJAT-52631 displayed a 50% biocontrol efficacy on loquat anthracnose at the fourth day after inoculation, but the crude lipopeptides not. The average lesion diameter of the whole-culture treated group was 5.62 mm, which was smaller than that of control group (6.81 mm). All the three types of lipopeptides including iturin A, fengycin, and surfactin A secreted from the strain FJAT-52631 exhibited antifungal activities. Among them, surfactin A displayed higher antifungal activity at a concentration of 1.25 mg/mL than other two lipopeptides even if at a concentration of 60 mg/mL. Thus, the results indicated that surfactin A produced by FJAT-52631 played a major role in the biocontrol of the loquat anthracnose. Scanning electron microscopy (SEM) observation revealed the structural deformities in the mycelia of C. acutatum. The above results suggested that the antifungal lipopeptides from B. velezensis FJAT-52631 would be potential in biocontrol against anthracnose disease of loquat caused by C. acutatum.

Synthesis and characterization of silver nanoparticles developed using a novel lipopeptide(s) biosurfactant and evaluating its antimicrobial and cytotoxic efficacy.

Novel bacterial lipopeptide(s) (LPs) biosurfactant obtained from Pseudomonas sp. OXDC12 were used to synthesizeLPs silver nanoparticles (LPs-Ag-NPs). LPs provided excellent colloidal stability by acting as a stabilizing/capping agent. The LPs-Ag-NPswere characterized using Field-Emission Scanning Electron Microscopy, Ultraviolet-visible spectroscopy,Fourier-transform infrared, Atomic force microscopy andX-Ray Diffraction. The formulation exhibited the production of monodisperse NPs with spherical morphology withan average diameter of 42.43 ± 5.2 nm.The metallic NP (LPs-Ag-NPs) formulation displayed remarkable antimicrobial/antifungal activity against Candida albicans (22.0 ± 1.3 mm), Fusarium oxysporum (28.0 ± 1.4 mm),Mucor sp. (26.0 ± 1.6 mm),Staphylococcus aureus MTCC96 (05.0 ± 0.6 mm), Salmonella typhimurium NCTC 74 (11.0 ± 0.2 mm), Klebsiellapneumnoniae (14.0 ± 0.3 mm) and Escherichiacoli MTCC1687 (12.6 ± 0.7 mm). The minimum inhibitory concentration (MIC) value was very less for LPs-Ag-NPs formulation when compared to purified LPs biosurfactant. LPs-Ag-NPs formulations showed cytotoxic activity against cancerous cells (L20B and RD; 80–94% at 80 µg/ mL) and were significantly less toxic against normal cells (PMC) showing only 22% cell reduction at 80 µg/ mL.In all, itwas concluded that capping the LPs on Ag-NPs successfully enhanced its antimicrobial and anti-cytotoxic properties.

Identification of bacterial lipopeptides as key players in IBS

ObjectivesClinical studies revealed that early-life adverse events contribute to the development of IBS in adulthood. The aim of our study was to investigate the relationship between prenatal stress (PS), gut...

Surfactin Bacterial Antiviral Lipopeptide Blocks In Vitro Replication of SARS-CoV-2

Despite great efforts have been made worldwide, the coronavirus disease 19 (COVID-19) still has not a definitive cure, although the availability of different vaccines are slowing down the transmission and severity. It has been shown that surfactin, a cyclic lipopeptide produced by Bacillus subtilis, is a molecule able to counteract both SARS-CoV-1, MERS-CoV and HCoV-229E coronaviruses. In this study the potential antiviral activity of surfactin against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was tested in vitro in a cellular model of infection. Our results show that 2 h treatment with surfactin is able to reduce SARS-CoV-2 infectivity on Vero E6 cells both at 24 h and after 7 days from viral inoculation, probably impairing the viral membrane integrity. Moreover, surfactin, at the concentrations used in our experimental settings, is not cytotoxic. We suggest surfactin as a new potential molecule against SARS-CoV-2, to be employed at least as a disinfectant.

Lipopeptides from Bacillus mojavensis I4 confer induced tolerance toward Rhizoctonia solani in potato (Solanum tuberosum)

Bacterial lipopeptides are known for their protective activity against plant pathogens. The antifungal activity of I4 lipopeptide was confirmed in vitro by a growth inhibition assay. In fact, the mycelium growth inhibition of R. solani in the presence of 5 mg/ml of I4 biosurfactants was about 76%. In this study, the protective effect of lipopeptides from Bacillus mojavensis I4 was tested in vitro against Rhizoctonia solani in potato plants. The treatment of potato plants with I4 lipopeptides (5 mg/ml), previously inoculated with 102 CFU/ml of R. solani was carried out for 15 days. Different physiological parameters such as plant morphology and growth, plant elongation, and chlorophyll content were higher in the inoculated and treated plants (IT) than in the inoculated untreated ones (IUT). Indeed, after 10 days of treatment, the application of I4 lipopeptide under biotic stress enhanced plant elongation and chlorophyll content by 75% and 65%, respectively, compared to the inoculated untreated plants (IUT). Moreover, the application of I4 lipopeptide biosurfactant under biotic stress caused a decrease in hydrogen peroxide (H2O2), malondialdehyde content (MDA) and enzymatic antioxidants activities (SOD, CAT and GPX) compared to untreated plants under the same conditions. Besides, The I4 lipopeptide treatment induced the expression of PR (pathogenesis-related) genes under control and biotic stress conditions and reduced plant diseases. Considered together, the data presented in this study demonstrated that biosurfactants produced by B. mojavensis I4 can be used to improve the biological control of potato pathogens.

Purification and characterization of a novel bacterial Lipopeptide(s) biosurfactant and determining its antimicrobial and cytotoxic properties

Lipopeptide(s) (LPs), a biomolecule containing a lipid head attached to a peptide tail, have different medicinal properties, which have paved the way for scientists interest in them. Their antimicrobial and anticancerous properties are the most explored. In this decade, many LPs were approved by the FDA to be used as drugs against different diseases. In the present study, LPs were extracted and purified from the Pseudomonas sp. OXDC12 strain. Different chromatographic techniques such as affinity chromatography (DEAE column) and size exclusion chromatography (Sephadex G-25) were used to purify the molecule. Later purified LPs were characterised via techniques such as TLC, HPLC, and MALDI-TOF and were found to be of a surfactant nature. The LPs biosurfactant substantially reduced the surface tension from 64 mN/m to ∼35 mN/m at a 30 mg/L critical micelle concentration (CMC). The LPs biosurfactant showed antifungal activity against Fusarium oxysporum (21.0 ± 2.4mm), Candida albicans (18.0 ± 1.3 mm) and Mucor sp. (23.0 ± 1.6 mm) and antibacterial activity against Staphylococcus aureus MTCC96 (4.0 ± 0.6), Salmonella typhimurium NCTC 74 (11.0 ± 0.2), Klebsiella pneumoniae (12.0 ± 0.3) and Escherichia coli MTCC1687 (8.6 ± 0.7) respectively. The purified LPs also showed cytotoxic and antiproliferative activities towards a few transformed cell lines, such as RD (IC50 32.47 µg/mL), Hep-2 C (IC50 35.48 µg/mL), Vero (IC50 27.96 µg/mL) and MCF-7 (IC50 46.01 µg/mL).

Biosíntesis inducida de fengicina y surfactina en una cepa de Bacillus amyloliquefaciens con actividad oomiceticida sobre zoosporas de Phytophthora capsica

A potential alternative to the use of chemical products with oomyceticidal action for the control of Phytophthora capsici in vegetables is the use of antimicrobial metabolites, biosynthesized in Bacillus species. The objective of this study was to induce the biosynthesis of lipopeptides in Bacillus amyloliquefaciens KX953161.1 by using glutamic acid, iron, cellulose, chitin, or inactive Colletotrichum spp. cells. The in vitro oomyceticidal effect of the bacterial lipopeptides on zoospores of Phytophthora capsici was evaluated. The lipopeptides identified and quantified in the crude extracts by high performance thin layer chromatography (HPTLC) were fengycin and surfactin. The bacterial culture with inactive fungal cells yielded the greatest biosynthesis of lipopeptides, at 1847.02± 11.8 and 2563.45± 18.4 μg/ml of fengycin and surfactin, respectively and the treatments that obtained lower production of these lipopeptides, were those to which iron and cellulose were added with 608.05 ± 22.6 and 903.74± 22.1; 563.31± 11.9 and 936.96± 41.1 μg/ml for fengicin and surfactin, respectively. The lipopeptide extracted showed 100% germination inhibition on zoospores of P. capsici, revealing encystment, malformations in the germ tube and cellular degradation. Lipopeptides have the potential to control P. capsici; however, the biosynthesis of these lipopeptides requires further study to determine their biological mode of action and optimize lipopeptide performance and profile.

Bacterial hitchhikers derive benefits from fungal housing

Fungi and bacteria are ubiquitous constituents of all microbiomes, yet mechanisms of microbial persistence in polymicrobial communities remain obscure. Here, we examined the hypothesis that specialized fungal survival structures, chlamydospores, induced by bacterial lipopeptides serve as bacterial reservoirs. We find that symbiotic and pathogenic gram-negative bacteria from non-endosymbiotic taxa enter and propagate in chlamydospores. Internalized bacteria have higher fitness than planktonic bacteria when challenged with abiotic stress. Further, tri-cultures of Ralstonia solanacearum, Pseudomonas aeruginosa, and Aspergillus flavus reveal the unprecedented finding that chlamydospores are colonized by endofungal bacterial communities. Our work identifies a previously unknown ecological role of chlamydospores, provides an expanded view of microbial niches, and presents significant implications for the persistence of pathogenic and beneficial bacteria.

Isolation, Identification and Characterization of Two Kinds of Deep-Sea Bacterial Lipopeptides Against Foodborne Pathogens.

Under multiple stresses of deep sea, many microorganisms have evolved potentials to produce different metabolites to cope with the stresses they face. In this study, we isolated a bacterial strain Bacillus sp. YJ17 from the deep-sea cold seep. Compared with commercial food preservative nisin, it showed broad and strong antibacterial activities against foodborne pathogens, including multiple resistant bacteria Pseudomonas aeruginosa PAO1 and methicillin-resistant Staphylococcus aureus (MRSA). The active agents were purified by reversed-phase high performance liquid chromatography (RP-HPLC). Analysis of high-energy collision induced dissociation mass spectrometry (HCD-MS) showed that the two active agents belong to family of fengycin and surfactin, and based on results of tandem mass spectrometry (HCD-MS/MS), the amino acid sequence of purified fengycin and surfactin might be Glu-Orn-Tyr-Thr-Glu-Val-Pro-Gln-Tyr-Ile and Glu-Leu/Ile-Leu/Ile-Leu/Ile-Val-Asp-Leu/Ile, respectively. Since the purified fengycin and surfactin exhibited strong inhibition against P. aeruginosa PAO1 and MRSA respectively, the inhibition mechanisms of fengycin against P. aeruginosa PAO1 and surfactin against MRSA were investigated by electron microscopy. After treatment with purified fengycin, the morphology of P. aeruginosa PAO1 became abnormal and aggregated together, and obvious cytoplasmic leakage was observed. After treatment with purified surfactin, the MRSA cells clustered together, and cell surface became rough and jagged. Further study showed that reactive oxygen species (ROS) accumulation and cell membrane damage occurred in P. aeruginosa PAO1 and MRSA after treated with fengycin and surfactin, respectively. Furthermore, typical ROS scavenging enzymes catalase (CAT) and superoxide dismutase (SOD) were also significantly reduced in P. aeruginosa PAO1 and MRSA after treated with fengycin and surfactin, respectively. Therefore, the inhibition mechanisms of fengycin against P. aeruginosa PAO1 and surfactin against MRSA are closely related with accumulation of ROS, which might be due to the decreased activity of CAT and SOD after treated with fengycin and surfactin, respectively. Overall, our study provides good candidates from the deep-sea environment to deal with foodborne pathogens, especially multidrug-resistant bacteria.

Microbe-Mediated Activation of Toll-like Receptor 2 Drives PDL1 Expression in HNSCC

Simple SummaryTumors use immunosuppressive signals to evade detection by the immune system. While recurrent and metastatic head and neck squamous cell carcinoma has historically carried a poor prognosis, therapies targeting the immunosuppressive PD1:PDL1 axis have improved survival in certain patients. Defining mechanisms regulating PDL1 in various contexts may inform refinement of immunotherapy protocols. We identified a role for Toll-like Receptor 2 (TLR2) signaling in driving PDL1 expression. In antigen-presenting cells, TLR2 functions to initiate response to pathogens, and it is overexpressed or genetically altered in some tumors. We found that the synthetic TLR2 ligand Pam3CSK4, as well as whole bacteria, induced PDL1 expression in specific HNSCC cell line models, suggesting that TLR2 may contribute to immune evasion in chronically inflamed tissues.As immunotherapies targeting the PDL1 checkpoint have become a mainstay of treatment for a subset of head and neck squamous cell carcinoma (HNSCC) patients, a detailed understanding of the mechanisms underlying PDL1-mediated immune evasion is needed. To elucidate factors regulating expression of PDL1 in HNSCC cells, a genome-wide CRISPR profiling approach was implemented to identify genes and pathways conferring altered PDL1 expression in an HNSCC cell line model. Our screen nominated several candidate PDL1 drivers, including Toll-like Receptor 2 (TLR2). Depletion of TLR2 blocks interferon-γ-induced PDL1 expression, and stimulation of TLR2 with either Staphylococcus aureus or a bacterial lipopeptide mimetic, Pam3CSK4, enhanced PDL1 expression in multiple models. The data herein demonstrate a role for TLR2 in modulating the expression of PDL1 in HNSCC models and suggest that microbiota may directly modulate immunosuppression in cancer cells. Our study represents a step toward disentangling the diverse pathways and stimuli regulating PDL1 expression in HNSCC and underscores a need for future work to characterize the complex microbiome in HNSCC patients treated with immunotherapy.

Bacillus siamensis CNE6- a multifaceted plant growth promoting endophyte of Cicer arietinum L. having broad spectrum antifungal activities and host colonizing potential

Exploration of endophytic bacteria with multiple plant growth promoting (PGP) attributes is considered as an eco-friendly and cost-effective alternative to agricultural chemicals for increasing crop productivity. In the present endeavor, healthy chickpea plants (Cicer arietinum L.) collected from district Birbhum, West Bengal, India were subjected for the isolation of endophytic bacteria having multifarious PGP properties. One potent endophytic Gram positive bacterial strain CNE6 was isolated from the nodule of chickpea and was identified as Bacillus siamensis based on 16S rDNA sequence homologies. The isolate showed a number of PGP properties like phosphate solubilization, IAA production, nitrogen fixation, hydroxamate type of siderophore production and ACC deaminase activities. The isolate CNE6 produced 33.27 ± 2.16 μg/mL of IAA in the presence of tryptophan. Production of IAA was also confirmed by HPLC analysis and it was found effective for inducing lateral root branching in chickpea. In addition, the isolate displayed significant antagonistic activity against a number of plant pathogenic fungi when tested by dual culture overlay and agar well diffusion assay. 50 % cell free supernatant of CNE6 was found effective for 60–80 % inhibition of radial growth of pathogenic fungi tested. Scanning electron microscopic observation revealed massive degradation of pathogenic fungal mycelia by the antifungal metabolites of CNE6. LC–MS analysis of bacterial lipopeptides suggested the production of antifungal antibiotics like surfactin, fengycin and iturin by the isolate. The presence of genes encoding antifungal lipopeptides was also confirmed by PCR amplification using specific primers. Green fluorescent protein (GFP) tagging of CNE6 using broad host range plasmid vector (pDSK-GFPuv) followed by colonization study indicated very good host colonization potential of the isolate and its probable movement through xylem vessels. Enhanced shoot and root length and chlorophyll content upon treatment with CNE6 as observed in in vivo pot experiments also supported the positive role of the endophytic isolate on overall development and growth of the chickpea plants. This is the first report of Bacillus siamensis as an endophyte of Cicer arietinum L. which can be successfully applied for improving the productivity of this crop plant.

A biogenic microbial biosurfactin that degrades difenoconazole fungicide with potential antimicrobial and oil displacement properties

Surfactin is a bacterial lipopeptide and an influential biosurfactant mainly known for excellent surfactant ability. The amphiphilic nature of surfactin helps it to sustain under hydrophobic and hydrophilic conditions. In this investigation, a bacterium strain (BTKU3) that produces biosurfactant were isolated from oil-contaminated soil. Based on the blue agar plate (Bap) assay, the BTKU3 strain was found to be promising for biosurfactant production. This strain was later identified as a Lysinibacillus sp. by 16S rRNA sequencing. The characteristics of extracted bacterial surfactin were evidenced by FTIR with the presence of amine, C–H, CO, CC, esters, thiocarbonyl and asymmetric aliphatic C–H stretch molecular structural groups. Further, the extracted bacterial biosurfactant material was subjected to Liquid Chromatography-Mass Spectroscopy (LCMS), and it was identified and confirmed as surfactin with an elution time of 3.1 min and m/z value of 1034. The emulsification and oil displacement tests further proved the surfactin ability with 83% of coconut oil emulsion index and 80 % oil displacement ability with diesel, respectively. Lysinibacillus sp. BTKU3 strain also proved its efficacy in the degradation of difenoconazole by utilizing a capacity of 9.1 μg ml−1. Thus, it is inferred that the Lysinibacillus sp. BTKU3 strain plays a significant role in the production of surfactin, which positively acts as an antimicrobial agent and reduces contaminants in polluted sites.

Pseudomonas Strains Induce Transcriptional and Morphological Changes and Reduce Root Colonization of Verticillium spp.

Phytopathogenic Verticillia cause Verticillium wilt on numerous economically important crops. Plant infection begins at the roots, where the fungus is confronted with rhizosphere inhabiting bacteria. The effects of different fluorescent pseudomonads, including some known biocontrol agents of other plant pathogens, on fungal growth of the haploid Verticillium dahliae and/or the amphidiploid Verticillium longisporum were compared on pectin-rich medium, in microfluidic interaction channels, allowing visualization of single hyphae, or on Arabidopsis thaliana roots. We found that the potential for formation of bacterial lipopeptide syringomycin resulted in stronger growth reduction effects on saprophytic Aspergillus nidulans compared to Verticillium spp. A more detailed analyses on bacterial-fungal co-cultivation in narrow interaction channels of microfluidic devices revealed that the strongest inhibitory potential was found for Pseudomonas protegens CHA0, with its inhibitory potential depending on the presence of the GacS/GacA system controlling several bacterial metabolites. Hyphal tip polarity was altered when V. longisporum was confronted with pseudomonads in narrow interaction channels, resulting in a curly morphology instead of straight hyphal tip growth. These results support the hypothesis that the fungus attempts to evade the bacterial confrontation. Alterations due to co-cultivation with bacteria could not only be observed in fungal morphology but also in fungal transcriptome. P. protegens CHA0 alters transcriptional profiles of V. longisporum during 2 h liquid media co-cultivation in pectin-rich medium. Genes required for degradation of and growth on the carbon source pectin were down-regulated, whereas transcripts involved in redox processes were up-regulated. Thus, the secondary metabolite mediated effect of Pseudomonas isolates on Verticillium species results in a complex transcriptional response, leading to decreased growth with precautions for self-protection combined with the initiation of a change in fungal growth direction. This interplay of bacterial effects on the pathogen can be beneficial to protect plants from infection, as shown with A. thaliana root experiments. Treatment of the roots with bacteria prior to infection with V. dahliae resulted in a significant reduction of fungal root colonization. Taken together we demonstrate how pseudomonads interfere with the growth of Verticillium spp. and show that these bacteria could serve in plant protection.