Control Strain Research Articles

Novel Lactobacillaceae strains and consortia to produce propionate-containing fermentates as biopreservatives.

Biopreservation refers to the use of natural or controlled microbial single strains or consortia, and/or their metabolites such as short-chain carboxylic acids (SCCA), to improve the shelf-life of foods. This study aimed at establishing a novel Lactobacillaceae-driven bioprocess that led to the production of the SCCA propionate through the cross-feeding on 1,2-propanediol (1,2-PD) derived from the deoxyhexoses rhamnose or fucose. When grown as single cultures in Hungate tubes, strains of Lacticaseibacillus rhamnosus preferred fucose over rhamnose and produced 1,2-PD in addition to lactate, acetate, and formate, while Limosilactobacillus reuteri metabolized 1,2-PD into propionate, propanol and propanal. Loigolactobacillus coryniformis used fucose to produce 1,2-PD and only formed propionate when supplied with 1,2-PD. Fermentates collected from batch fermentations in bioreactor using two-strain consortia (L. rhamnosus and L. reuteri) or fed-batch fermentations of single strain cultures of L. coryniformis with rhamnose contained mixtures of SCCA consisting of mainly lactate and acetate and also propionate. Synthetic mixtures that contained SCCA at concentrations present in the fermentates were more antimicrobial against Salmonella enterica if propionate was present. Together, this study (i) demonstrates the potential of single strains and two-strain consortia to produce propionate in the presence of deoxyhexoses extending the fermentation metabolite profile of Lactobacillaceae, and (ii) emphasizes the potential of applying propionate-containing fermentates as biopreservatives.

Effectiveness of hydrogen peroxide wipes for surface disinfection in healthcare facilities.

The correct method of surface disinfection in hospitals is an essential tool in the fight against the spread of healthcare-associated infections caused by multi-resistant microorganisms. Currently, there are many disinfectants on the market that can be used against different microorganisms. However, the effectiveness of different active molecules is controversial in the literature. The aim of this study was to evaluate the effectiveness of wipes based on hydrogen peroxide (1.0 %) and highly specific plant-based surfactants, contained in H2O2TM (Hi-speed H2O2TM) products, against some hospital-associated microorganisms. The effectiveness of the wipes was tested against nosocomial and control strains of methicillin-resistant Staphylococcus aureus, carbapenem-resistant Pseudomonas aeruginosa, Klebsiella pneumoniae carbapenemase, Aspergillus fumigatus and Candida parapsilosis. Specifically, in vitro activity was assessed using three different techniques: stainless steel surface testing, surface diffusion testing and well diffusion test. The three different methods tested confirm the wipes' good effectiveness against the most common multi-resistant bacteria and against fungi. These data show that the tested wipes could be a valid adjunct to the disinfection process and could assist in the prevention of healthcare-associated infections.

Synergistic use of anti-inflammatory ketorolac and gentamicin to target staphylococcal biofilms

BackgroundWhile antibiotics remain our primary tools against microbial infection, increasing antibiotic resistance (inherent and acquired) is a major detriment to their efficacy. A practical approach to maintaining or reversing the efficacy of antibiotics is the use of other commonly used therapeutics, which show synergistic antibacterial action with antibiotics. Here, we investigated the extent of antibacterial synergy between the antibiotic gentamicin and the anti-inflammatory ketorolac regarding the dynamics of biofilm growth, the rate of acquired resistance, and the possible mechanism of synergy.MethodsControl (ATCC 12600, ATCC 35984) and clinical strains (L1101, L1116) of Staphylococcus aureus and Staphylococcus epidermidis with varying antibiotic susceptibility profiles were used in this study to simulate implant-material associated low-risk and high-risk biofilms in vitro. The synergistic action of gentamicin sulfate (GS) and ketorolac tromethamine (KT), against planktonic staphylococcal strains were determined using the fractional inhibitory concentration measurement assay. Nascent (6 h) and established (24 h) biofilms were grown on 316L stainless steel plates and the synergistic biofilm eradication activity was determined and characterized using adherent bacteria count, minimum biofilm eradication concentration (MBEC) measurement for GS, visualization by live/dead imaging, scanning electron microscopy, gene expression of biofilm-associated genes, and bacterial membrane fluidity assessment.ResultsGentamicin-ketorolac (GS-KT) combination demonstrated synergistic antibacterial action against planktonic Staphylococci. Control and clinical strains showed distinct biofilm growth dynamics and an increase in biofilm maturity was shown to confer further resistance to gentamicin for both ‘low-risk’ and ‘high-risk’ biofilms. The addition of ketorolac enhanced the antibiofilm activity of gentamicin against acquired resistance in staphylococcal biofilms. Mechanistic studies revealed that the synergistic action of gentamicin–ketorolac interferes with biofilm morphology and subverts bacterial stress response altering bacterial physiology, membrane dynamics, and biofilm properties.ConclusionThe results of this study have a significant impact on the local administration of antibiotics and other therapeutic agents commonly used in the prevention and treatment of orthopaedic infections. Further, these results warrant the study of synergy for the concurrent or sequential administration of non-antibiotic drugs for antimicrobial effect.

Metabolic perturbation of Streptomyces albulus by introducing NADP-dependent glyceraldehyde 3-phosphate dehydrogenase.

The available resources of Streptomyces represent a valuable repository of bioactive natural products that warrant exploration. Streptomyces albulus is primarily utilized in the industrial synthesis of ε-poly-L-lysine (ε-PL). In this study, the NADP-dependent glyceraldehyde 3-phosphate dehydrogenase (GapN) from Streptococcus mutans was heterologously expressed in S. albulus CICC11022, leading to elevated intracellular NADPH levels and reduced NADH and ATP concentrations. The resulting perturbation of S. albulus metabolism was comprehensively analyzed using transcriptomic and metabolomic methodologies. A decrease in production of ε-PL was observed. The expression of gapN significantly impacted on 23 gene clusters responsible for the biosynthesis of secondary metabolites. A comprehensive analysis revealed a total of 21 metabolites exhibiting elevated levels both intracellularly and extracellularly in the gapN expressing strain compared to those in the control strain. These findings underscore the potential of S. albulus to generate diverse bioactive natural products, thus offering valuable insights for the utilization of known Streptomyces resources through genetic manipulation.

Comparative genomic analysis of uropathogenic Escherichia coli strains from women with recurrent urinary tract infection.

Recurrent urinary tract infections (RUTIs) caused by uropathogenic Escherichia coli are costly public health problems impacting patients' quality of life. In this work, a comparative genomics analysis of three clinical RUTI strains isolated from bladder biopsy specimens was performed. One hundred seventy-two whole genomes of urinary tract E. coli strains were selected from the NCBI database. The search for virulence factors, fitness genes, regions of interest, and genetic elements associated with resistance was manually carried out. The phenotypic characterization of antibiotic resistance, haemolysis, motility, and biofilm formation was performed. Moreover, adherence and invasion assays with human bladder HTB-5 cells, and transmission electron microscopy (TEM) were performed. The UTI-1_774U and UTI-3_455U/ST1193 strains were associated with the extraintestinal pathotypes, and the UTI-2_245U/ST295 strain was associated with the intestinal pathotype, according to a phylogenetic analysis of 172 E. coli urinary strains. The three RUTI strains were of clinical, epidemiological, and zoonotic relevance. Several resistance genes were found within the plasmids of these strains, and a multidrug resistance phenotype was revealed. Other virulence genes associated with CFT073 were not identified in the three RUTI strains (genes for type 1 and P fimbriae, haemolysin hlyA, and sat toxin). Quantitative adherence analysis showed that UTI-1_774U was significantly (p < 0.0001) more adherent to human bladder HTB-5 cells. Quantitative invasion analysis showed that UTI-2_245U was significantly more invasive than the control strains. No haemolysis or biofilm activity was detected in the three RUTI strains. The TEM micrographs showed the presence of short and thin fimbriae only in the UTI-2_245U strain. The high variability and genetic diversity of the RUTI strains indicate that are a mosaic of virulence, resistance, and fitness genes that could promote recurrence in susceptible patients.

Possibility of transfer and activation of 'silent' tetracycline resistance genes among Enterococcus faecalis under high-pressure processing

In this study, the tetracycline resistance of Enterococcus faecalis strains isolated from food was determined and molecular analyses of the resistance background were performed by determining the frequency of selected tetracycline resistance genes. In addition, the effect of high-pressure stress (400 and 500 MPa) on the expression of selected genes encoding tetracycline resistance was determined, as well as changes in the frequency of transfer of these genes in isolates showing sensitivity to tetracyclines. In our study, we observed an increase in the expression of genes encoding tetracyclines, especially the tet(L) gene, mainly under 400 MPa pressure. The study confirmed the possibility of transferring genes encoding tetracyclines such as tet(M), tet(L), tet(K), tet(W) and tet(O) by horizontal gene transfer in both control strains and exposed to high-pressure. Exposure of the strains to 400 MPa pressure had a greater effect on the possibility of gene transfer and expression than the application of a higher-pressure. To our knowledge, this study for the first time determined the effect of high-pressure stress on the expression of selected genes encoding tetracycline resistance, as well as the possibility and changes in the frequency of transfer of these genes in Enterococcus faecalis isolates showing sensitivity to tetracyclines and possessing silent genes. Due to the observed possibility of increased expression of some of the genes encoding tetracycline resistance and the possibility of their spread by horizontal gene transfer to other microorganisms in the food environment, under the influence of high-pressure processing in strains phenotypically susceptible to this antibiotic, it becomes necessary to monitor this ability in isolates derived from foods.

Characterization of the intracellular neurexin interactome by in vivo proximity ligation suggests its involvement in presynaptic actin assembly.

Neurexins are highly spliced transmembrane cell adhesion molecules that bind an array of partners via their extracellular domains. However, much less is known about the signaling pathways downstream of neurexin's largely invariant intracellular domain (ICD). Caenorhabditis elegans contains a single neurexin gene that we have previously shown is required for presynaptic assembly and stabilization. To gain insight into the signaling pathways mediating neurexin's presynaptic functions, we employed a proximity ligation method, endogenously tagging neurexin's intracellular domain with the promiscuous biotin ligase TurboID, allowing us to isolate adjacent biotinylated proteins by streptavidin pull-down and mass spectrometry. We compared our experimental strain to a control strain in which neurexin, endogenously tagged with TurboID, was dispersed from presynaptic active zones by the deletion of its C-terminal PDZ-binding motif. Selection of this control strain, which differs from the experimental strain only in its synaptic localization, was critical to identifying interactions specifically occurring at synapses. Using this approach, we identified both known and novel intracellular interactors of neurexin, including active zone scaffolds, actin-binding proteins (including almost every member of the Arp2/3 complex), signaling molecules, and mediators of RNA trafficking, protein synthesis and degradation, among others. Characterization of mutants for candidate neurexin interactors revealed that they recapitulate aspects of the nrx-1(-) mutant phenotype, suggesting they may be involved in neurexin signaling. Finally, to investigate a possible role for neurexin in local actin assembly, we endogenously tagged its intracellular domain with actin depolymerizing and sequestering peptides (DeActs) and found that this led to defects in active zone assembly. Together, these results suggest neurexin's intracellular domain may be involved in presynaptic actin-assembly, and furthermore highlight a novel approach to achieving high specificity for in vivo proteomics experiments.

Effects of small heat shock proteins from thermotolerant bacteria on the stress resistance of Escherichia coli to temperature, pH, and hyperosmolarity

Small heat shock proteins (HSPs), such as HSP20, represent cellular thermal resistance mechanisms, to avoid protein aggregation at elevated temperatures. Recombinantly expressed HSP20s serve as a molecular tool for improving the tolerance of living cells to various physical and chemical stressors. Here, we aimed to heterologously express 18 HSP20s from 12 thermotolerant bacteria in Escherichia coli and evaluate their effects on various physical and chemical cellular stresses. Seventeen HSP20s were successfully expressed as soluble proteins. Recombinant E. coli cells were subjected to heat, cold, acidic, alkaline, and hyperosmolar stress to evaluate the effects of HSP20 proteins on stress resistance. Notably, the overexpression of 15 HSP20s enhanced the stress resistance of E. coli compared to that of the control strain. In particular, HSPs from Tepidimonas sediminis and Oceanithermus profundus improved the stress tolerance of E. coli under all tested conditions. In addition, E. coli harboring HSP20 from T. sediminis retained cell viability even after heat treatment at 52 °C for 5 days. To our knowledge, this is the first report of E. coli tolerance to prolonged (> 100 h) high-temperature stress. These findings indicate the potential of thermotolerant HSPs as molecular tools for improving stress tolerance in E. coli.

Screening and diversity of culturable HNAD bacteria in the MBR sewage treatment system.

The activated sludge was collected from the Membrane BioReactor (MBR) pool of the sewage treatment system of Sanxing Town, Jintang County, Chengdu, to obtain a good population of heterotrophic nitrifying/aerobic denitrifying (HNAD) bacteria. After undergoing enrichment, isolation, and purification, the HNAD bacteria were selected using the pure culture method. The 16S rDNA molecular technology was used to determine the taxonomy of bacteria. The heterophic nitrifying ability and denitrification capacity of HNAD strains was ascertained through their growth characteristics in heterotrophic nitrification and denitrification media. The results showed that 53 HNAD strains selected from the MBR pool belonged to 2 phyla, 3 classes, 6 orders, 6 families, and 7 genera, with 26 species. Acinetobacter was the largest and dominant genus. Among these, strains numbered (bacterial strain) SW21HD14, SW21HD17, and SW21HD18 were potentially new species in the Acinetobacter genus. Each HNAD strain showed a significant heterotrophic nitrifying and aerobic denitrifying efficiency compared with the control strain (P < 0.05). Specifically, 10 strains demonstrated ammonia nitrogen degradation of greater than 70 mg·L-1 and 9 strains demonstrated nitrate nitrogen degradation above 150 mg·L-1. The HNAD bacteria, which were selected from the MBR pool of sewage treatment system of the Sanxing Town sewage treatment plant, exhibited rich diversity and strong nitrogen removal ability. These findings offered an effective strain source and theoretical basis for implementing biological denitrification technology that involves synchronous nitrification and denitrification.

Efficient Screening and Enhanced Exopolysaccharide Production by Functional Lactic Acid Bacteria (LAB) in Lactose Supplemented Media

Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) can be considered as natural biological thickeners that have attracted considerable attention in the food industry. This study aimed to evaluate and select potentially EPS-producing strains LAB and to assess the influence of carbon source and aeration on EPS production. Nine LAB strains were assessed as potential EPS producers, and Rahnella aquatilis ATCC 55046 was employed as the positive control strain for EPS. The compaction test and the observation of viscous colonies in a solid medium did not yield sufficient evidence for the presence of EPS. The assessment of capsules through staining provided evidence of EPS presence only for Rahnella aquatilis ATCC 55046. The EPS yield was subsequently assessed in De-Man Rogosa and Sharpe (MRS) broth medium supplemented with 2% (w/w) fructose (MRS-f) or lactose (MRS-l), as well as in whey (Whey) and whey supplemented with 2% (w/w) lactose (Whey-l). The EPS production in the various culture media under study ranged from 194 to 1,187 mg of EPS/g of polymer dry mass (PDM). These results suggest that the culture medium and carbon sources had an impact on the EPS production of the different strains. Bifidobacterium animalisBb12 achieved the highest EPS production in MRS-f. In the case of MRS-l, the control strain recorded the highest EPS value, along with Lactobacillus acidophilus LAC-1. Regarding Whey, Lentilactobacillus Kefir NCFB 2753 exhibited the highest EPS production, while in Whey-l, Lacticaseibacillus paracasei LCS-1 emerged as the top performer in terms of EPS production. This suggests that certain strains exhibit potential for use in the production of novel fermented EPS products, whether dairy or non-dairy.

Class VI G protein-coupled receptors in Aspergillus oryzae regulate sclerotia formation through GTPase-activating activity

G protein-coupled receptors (GPCRs) comprise the largest family of transmembrane receptors in eukaryotes that sense and transduce extracellular signals into cells. In Aspergillus oryzae, 16 canonical GPCR genes are identified and classified into nine classes based on the sequence similarity and proposed functions. Class VI GPCRs (AoGprK-1, AoGprK-2, and AoGprR in A. oryzae), unlike other GPCRs, feature a unique hybrid structure containing both the seven transmembrane (7-TM) and regulator of G-protein signaling (RGS) domains, which is not found in animal GPCRs. We report here that the mutants with double or triple deletion of class VI GPCR genes produced significantly increased number of sclerotia compared to the control strain when grown on agar plates. Interestingly, complementation analysis demonstrated that the expression of the RGS domain without the 7-TM domain is sufficient to restore the phenotype. In line with this, among the three Gα subunits in A. oryzae, AoGpaA, AoGpaB, and AoGanA, forced expression of GTPase-deficient mutants of either AoGpaA or AoGpaB caused an increase in the number of sclerotia formed, suggesting that RGS domains of class VI GPCRs are the negative regulators of these two GTPases. Finally, we measured the expression of velvet complex genes and sclerotia formation-related genes and found that the expression of velB was significantly increased in the multiple gene deletion mutants. Taken together, these results demonstrate that class VI GPCRs negatively regulate sclerotia formation through their GTPase-activating activity in the RGS domains.Key points• Class VI GPCRs in A. oryzae regulate sclerotia formation in A. oryzae• RGS function of class VI GPCRs is responsible for regulation of sclerotia formation• Loss of class VI GPCRs resulted in increased expression of sclerotia-related genes

Engineering an Artificial Pathway to Improve the Bioconversion of Lysine into Chiral Amino Alcohol 2-Hydroxycadaverine Using a Semi-Rational Design

Amino alcohols are important compounds that are widely used in the polymer and pharmaceutical industry, particularly when used as chiral scaffolds in organic synthesis. The hydroxylation of polyamide polymers may allow crosslinking between molecular chains through the esterification reactions of hydroxyl and carboxyl groups. Therefore, this may alter the functional properties of polyamide polymers. 2-hydroxycadaverine (2HyC), as a new type of chiral amino alcohol, has potential applications in the pharmaceutical, chemical, and polymer industries. Currently, 2HyC production has only been realized via pure enzyme catalysis or two-stage whole-cell biocatalysis, which faces great challenges for scale-up production. However, the use of a cell factory is very promising for the production of 2HyC in industrial applications. Here, we designed and constructed a promising artificial pathway in Escherichia coli for producing 2HyC from biomass-derived lysine. This biosynthesis route expands the lysine catabolism pathway and employs two enzymes to sequentially convert lysine into 2HyC. However, the catalytic activity of wild-type pyridoxal phosphate-dependent decarboxylase from Chitinophage pinensis (DCCp) toward 3-hydroxylysine is lower, resulting in the lower production of 2HyC. Thus, the higher catalytic activity of DCCp is desired for low-cost and expanded industrial applications of 2HyC. To improve the catalytic activity of DCCp, a mutant library of DCCp was first built using a semi-rational design. The Kcat/Km of mutant DCCp (R53D/V94I) increased by 63%. A titer of 359 mg/L 2HyC was produced in shake flasks, with a 2HyC titer increase of 54% compared to control strain ML101. The results show that the production of 2HyC was effectively increased through a semi-rational design strategy. These findings lay the foundation for the development and utilization of renewable resources to produce 2HyC in microorganisms via an efficient, green, and sustainable biosynthetic strategy for further industrial application.

Aspergillus oryzae PrtR alters transcription of individual peptidase genes in response to the growth environment

Aspergillus oryzae PrtR is an ortholog of the transcription factor PrtT, which positively regulates the transcription of extracellular peptidase genes in Aspergillus niger and Aspergillus fumigatus. To identify the genes under the control of PrtR and elucidate its regulatory mechanism in A. oryzae, prtR gene disruption mutants were generated. The control strain clearly showed a halo on media containing skim milk as the nitrogen source, whereas the ΔprtR strain formed a smaller halo. Measurement of acid peptidase activity revealed that approximately 84% of acidic endopeptidase and 86% of carboxypeptidase activities are positively regulated by PrtR. As the transcription of the prtR gene varied depending on culture conditions, especially with or without a protein substrate, it was considered that its transcription would be regulated in response to a nitrogen source. In addition, contrary to previous expectations, PrtR was found to act both in promoting and repressing the transcription of extracellular peptidase genes. The mode of regulation varied from gene to gene. Some genes were regulated in the same manner in both liquid and solid cultures, whereas others were regulated in different ways depending on the culture conditions. Furthermore, PrtR has been suggested to regulate the transcription of peptidase genes that are closely associated with other transcription factors.Key points• Almost all peptidase genes in Aspergillus oryzae are positively regulated by PrtR• However, several genes are regulated negatively by PrtR• PrtR optimizes transcription of peptidase genes in response to culture conditions

Screening of core microorganisms in healthy and diseased peaches and effect evaluation of biocontrol bacteria (Burkholderia sp.)

Biological antagonists serve as the most important green alternatives to chemical fungicides, a class of microorganism that inhibits the growth of pathogenic fungi to reduce fruit incidence. In this paper, healthy and diseased peach fruit was selected for amplicon sequencing of the epiphytic microbiota on their surface to obtain a comprehensive understanding. Community structure, diversity and LefSe analysis were performed to screen Acetobacter, Muribaculaceae and Burkholderia as the core bacteria, Mycosphaerella, Penicillium and Alternaria as the core fungi, they showed significant differences and were highly enriched. Two strains fungi (Penicillium K3 and N1) and one strain antagonistic bacteria (Burkholderia J2) were isolated. The in intro test results indicated the bacterial suspension, fermentation broth and volatile organic compounds of antagonistic bacteria J2 were able to significantly inhibit pathogen growth. In vivo experiments, peach was stored at 28 °C for 6 days after different treatments, and samples were taken every day. It was found that Burkholderia J2 enhanced peach resistance by increasing the activities of antioxidant-related enzymes such as SOD, POD, PAL, PPO, GR, MDHAR, and DHAR. The results improved that Burkholderia J2 has great biocontrol potential and could be used as a candidate strain for green control of blue mold.

Multi-modular metabolic engineering and efflux engineering for enhanced lycopene production in recombinant Saccharomyces cerevisiae.

In this research, lycopene production in yeast was markedly enhanced by integrating a multi-modular approach, acetate signaling-based down-regulation of competitive pathways, and an efflux optimization strategy.

Rhizoviticin is an alphaproteobacterial tailocin that mediates biocontrol of grapevine crown gall disease.

Tailocins are headless phage tail structures that mediate interbacterial antagonism. Although the prototypical tailocins, R- and F-pyocins, in Pseudomonas aeruginosa, and other predominantly R-type tailocins have been studied, their presence in Alphaproteobacteria remains unexplored. Here, we report the first alphaproteobacterial F-type tailocin, named rhizoviticin, as a determinant of the biocontrol activity of Allorhizobium vitis VAR03-1 against crown gall. Rhizoviticin is encoded by a chimeric prophage genome, one providing transcriptional regulators and the other contributing to tail formation and cell lysis, but lacking head formation genes. The rhizoviticin genome retains a nearly intact early phage region containing an integrase remnant and replication-related genes critical for downstream gene transcription, suggesting an ongoing transition of this locus from a prophage to a tailocin-coding region. Rhizoviticin is responsible for the most antagonistic activity in VAR03-1 culture supernatant against pathogenic A. vitis strain, and rhizoviticin deficiency resulted in a significant reduction in the antitumorigenic activity in planta. We identified the rhizoviticin-coding locus in eight additional A. vitis strains from diverse geographical locations, highlighting a unique survival strategy of certain Rhizobiales bacteria in the rhizosphere. These findings advance our understanding of the evolutionary dynamics of tailocins and provide a scientific foundation for employing rhizoviticin-producing strains in plant disease control.

The role of areA in lipid accumulation in high lipid-producing fungus Mucor circinelloides WJ11

In the oleaginous fungus Mucor circinelloides, lipid accumulation is regulated by nitrogen metabolism, which is regulated by the areA gene, a member of the GATA zinc finger transporter family and a major regulator for nitrogen metabolism. However, the role of areA in lipid accumulation in this fungus has not been reported. In order to explore the regulatory effect of areA gene on nitrogen metabolism and lipid accumulation in M. circinelloides, we constructed areA gene knockout and overexpression strains. Then, the recombinant strains were cultured and their biochemical indexes were measured. Simultaneously, transcriptomic studies on the recombinant strains were conducted to infer the regulatory mechanism of areA. The results showed that the areA knockout strain accumulated more lipid, which is 42 % higher than the control. While the areA overexpressing strain obtained the higher biomass accumulation (23 g/L) and used up the nitrogen source in the medium earlier than the control strain and knockout strain. Transcriptome data analysis showed that nr and nit-6 genes related to nitrogen metabolism were up-regulated. And the expression levels of key genes acc and aclY were higher in the areA knockout strain than others, which was positively correlated with the increased lipid accumulation. In addition, in knockout strains, protein catabolism tended to provide substrates for the lipid production, and the expression levels of the related genes were also higher than others. These results indicated that the areA gene not only controls the transcription level of genes related to nitrogen metabolism but also affects lipid accumulation.

Controllable strain-driven topological phase transition and dominant surface-state transport in HfTe5

The fine-tuning of topologically protected states in quantum materials holds great promise for novel electronic devices. However, there are limited methods that allow for the controlled and efficient modulation of the crystal lattice while simultaneously monitoring the changes in the electronic structure within a single sample. Here, we apply significant and controllable strain to high-quality HfTe5 samples and perform electrical transport measurements to reveal the topological phase transition from a weak topological insulator phase to a strong topological insulator phase. After applying high strain to HfTe5 and converting it into a strong topological insulator, we found that the resistivity of the sample increased by 190,500% and that the electronic transport was dominated by the topological surface states at cryogenic temperatures. Our results demonstrate the suitability of HfTe5 as a material for engineering topological properties, with the potential to generalize this approach to study topological phase transitions in van der Waals materials and heterostructures.

Colonization and population dynamics of total, viable, and culturable cells of two biological control strains applied to apricot, peach, and grapevine crops.

The ecological fitness of the biological control strains Bacillus velezensis A17 and Lactiplantibacillus plantarum PM411 was evaluated in different crops, geographical zones, and growing seasons. Both strains (2 g L-1 of dried formulation) were spray-inoculated on apricot trees, peach trees, and grapevines. Depending on the crop, flowers, fruits, and leaves were picked at several sampling time points. The population dynamics of viable, viable but non-culturable, and dead cells were studied by comparing viability qPCR (v-qPCR), qPCR, and plate counting estimations. A17 showed high survival rates in apricot, peach, and grapevine organs. The A17 viability was confirmed since qPCR and v-qPCR estimations did not significantly differ and were rather constant after field applications. However, higher population levels were estimated by plate counting due to the non-selective characteristics of the medium used. The viability of PM411 was constrained by plant organ, crop, and climate conditions, being higher in apricot than in grapevine. PM411 survival declined after field application, indicating difficulties in its establishment. The PM411 population level was made up of dead, culturable, and viable but non-culturable cells since significant differences between the three methods were observed. In conclusion, A17 and PM411 differ strongly in their survival in grapevine, peach, and apricot.

Virulence profile of Candida spp. isolated from an anaerobic biodigester supplied with dairy cattle waste

Anaerobic biodigesters play a crucial role in enhancing animal waste management. However, the presence of pathogens in the biodigestion process poses a significant concern. Candida spp., a widespread fungus known for its opportunistic nature and adaptability to diverse environmental conditions, including reciprocal transmission between humans and animals, is one such pathogen of concern. Therefore, it is imperative to assess the virulence profile of Candida spp. originating from anaerobic biodigestion processes. Here we demonstrate that strains isolated from the biodigestion process of dairy cattle waste exhibit noteworthy virulence mechanisms, surpassing the virulence of clinical control strains. After we identified strains from affluent, effluent, and biofertilizer, we observed that all analyzed isolates produced biofilm. Additionally, a substantial proportion of these isolates demonstrated phospholipase production, while only a few strains exhibited protease production. Furthermore, all strains exhibited resistance or dose-dependent responses to amphotericin B and itraconazole, with the majority displaying resistance to fluconazole. In the in vivo test, we observed a significant correlation (p < 0.05) between the LT50 and biofilm formation as well as hyphae/pseudohyphae production. Additionally, some isolates demonstrated a quicker nematode-killing capacity compared to clinical controls. Our findings underscore the considerable pathogenic potential of certain Candida species present in the dynamics of anaerobic biodigestion. Importantly, the anaerobic biodigester system did not eliminate Candida strains from dairy cattle waste, highlighting the need for caution in utilizing biodigester products. We advocate for further studies to explore the virulence of other microorganisms in various animal production contexts. Furthermore, our results emphasize the urgency of enhancing waste treatment methods to effectively eliminate pathogens and curb their potential dissemination.