A possible mechanism of farnesol tolerance in C. albicans biofilms implemented by activating the PKC signalling pathway and stabilizing ROS levels

Introduction. Biofilms are the natural growth state for most microorganisms. C. albicans biofilms are composed of multiple cell types (round budding yeast-form cells, oval pseudohyphal cells, and elongated hyphal cells) encased in an extracellular matrix. C. albicans biofilms are notorious for resistance to antimicrobial treatments, a property that might be determined by complex mechanisms. Exogenous farnesol exerts a certain antifungal activity against C. albicans with medical implications. Different from other microbes, C. albicans biofilms can tolerate exogenous farnesol at high concentration with some cells still surviving and even maintaining proliferation, but the mechanism is unclear. Hypothesis. The study hypothesizes that C. albicans resists farnesol by activating the PKC signalling pathway. Aim. The study aims to discuss the molecular mechanism of C. albicans resistance to farnesol. Methodology. The ROS levels, the genes and proteins of the PKC pathway were compared between the farnesol-tolerant and non-tolerant groups using ROS levels assay, q-RT PCR and Western blot, respectively. Further, the mutant strains (pkc1Δ/Δ and mkc1Δ/Δ) were constructed, then the survival rates and ROS levels of biofilms exposed to farnesol were compared between mutant and wild strains. The morphological changes were observed using TEM. Results. The survival rates of C. albicans biofilms decreased rapidly under the lower concentration of farnesol (P<0.05), and kept stable (P>0.05) as the concentration rose up to 200 µM. The gene expression of the PKC pathway increased, while ROS levels remained stable and even decreased in the farnesol-tolerant biofilms, compared with those in the farnesol-nontolerant biofilms after farnesol treatment (P<0.05); pkc1 and mkc1 were significantly upregulated by C. albicans during the development of biofilm tolerance to farnesol. The cell wall and cytoplasm of pkc1Δ/Δ and mkc1Δ/Δ were damaged, and the ROS level increased (P<0.05); meanwhile, the survival rate of biofilms decreased compared with that of wild-type strain under the same farnesol concentrations (P<0.05). ROS inhibitors reversed these changes in pkc1Δ/Δ and mkc1Δ/Δ when the mutant strains exposed to farnesol. Conclusion. C. albicans biofilms can tolerate high concentrations of farnesol by activating pkc1 and mkc1 of the PKC pathway and stabilizing ROS levels. The pkc1 and mkc1 are two key genes regulated by C. albicans in the process of biofilm tolerance to farnesol.

Effect of Various Strains of Lactobacillus buchneri on the Fermentation Quality and Aerobic Stability of Corn Silage

The aerobic deterioration of silage nutrients is inevitable in tropical countries, causing negative consequences in animal production systems. Aiming to minimize the losses, the effects of Lactobacillus buchneri strains on fermentation profile and aerobic stability of corn silages were evaluated. The experiment was conducted under a completely randomized design with 13 treatments and three replicates. The treatments were noninoculated, commercial L. buchneri (CI), and 11 wild strains of L. buchneri: LB-56.1, LB-56.2, LB-56.4, LB-56.7, LB-56.8, LB-56.9, LB-56.21, LB-56.22, LB-56.25, LB-56.26, and LB-56.27. The treatments could be divided into three different groups according to silage pH and acetic acid concentration. Silages inoculated with LB-56.1, LB-56.4, and LB-56.9 presented higher pH, whereas intermediate values were observed for LB-56.2, LB-56.7, and LB-56.8. The highest acetic acid production was observed for LB-56.1 and LB-56.7. On the other hand, lowest concentrations were found for CI, LB-56.22, LB-56.25, LB-56.26, and LB-56.27. Higher amounts of NH3–N were observed for LB-56.8, LB-56.21, LB-56.22, and LB-56.27 silages than others. Silage inoculation with CI, LB-56.1, LB-56.2, LB-56.4, LB-56.8, LB-56.9, and LB-56.25 strains had higher aerobic stability than others (59.7 vs. 41.2 h). The L. buchneri strains LB-56.1, LB-56.2, LB-56.4, LB-56.8, LB-56.9, and LB-56.25 provided potential features to improve the aerobic stability of corn silage.

Online Advanced Bacterial Identification Software, an Original Tool for Phenotypic Bacterial Identification

The objective of the study is to present and validate an original online Advanced Bacterial Identification Software, ABIS, by comparison to a commercially available, standardized identification system, API strips and apiweb™ bioMerieux software. Methods and results: presentation of ABIS online software, phenotypic bacterial identification of 16 reference strains and 123 wild isolates by ABIS and apiweb TM bioMerieux software and comparative analysis of results. Closed results were obtained (same taxa) for reference and wild strains of Enterobacteriaceae, Pasteurellaceae, Bacillaceae, Lactobacillaceae, Staphylococcaceae, Streptococcaceae, and other. Conclusions: Apiweb™ confirmed the results of ABIS, overall, average identification percent for ABIS being 91.8% and 90.4% for apiweb TM. ABIS online is a powerful tool for microbiology lab and the Encyclopedia connection provides essential information about the ecological significance, pathology and other features of the identified strains.

Developing an empirical model for spillover and emergence: Orsay virus host range in Caenorhabditis

A lack of tractable experimental systems in which to test hypotheses about the ecological and evolutionary drivers of disease spillover and emergence has limited our understanding of these processes. Here we introduce a promising system: Caenorhabditis hosts and Orsay virus, a positive-sense single-stranded RNA virus that naturally infects C. elegans. We assayed the susceptibility of species across the Caenorhabditis tree and found 21 of 84 wild strains belonging to 14 of 44 species to be susceptible to Orsay virus. Confirming patterns documented in other systems, we detected effects of host phylogeny on susceptibility. We then tested whether susceptible strains were capable of transmitting Orsay virus by transplanting exposed hosts and determining whether they transmitted infection to conspecifics during serial passage. We found no evidence of transmission in 10 strains (virus undetectable after passaging), evidence of low-level transmission in 5 strains (virus lost between passage 1 and 5), and evidence of sustained transmission in 6 strains (including all 3 experimental C. elegans strains). Transmission was associated with host phylogeny and with viral amplification in exposed populations. Variation in Orsay virus susceptibility and transmission among Caenorhabditis species suggests that the system could be powerful for studying spillover and emergence.

An Autochthonous Acidithiobacillus ferrooxidans Metapopulation Exploited for Two-Step Pyrite Biooxidation Improves Au/Ag Particle Release from Mining Waste

Pyrite bio-oxidation by chemolithotrophic acidophile bacteria has been applied in the mining industry to bioleach metals or to remove pyritic sulfur from coal. In this process, it is desirable to use autochthonous and already adapted bacteria isolated directly from the mining sites where biomining will be applied. Bacteria present in the remnant solution from a mining company were identified through cloning techniques. For that purpose, we extracted total RNA and performed reverse transcription using a novel pair of primers designed from a small region of the 16S gene (V1–V3) that contains the greatest intraspecies diversity. After cloning, a high proportion of individuals of the strains ATCC-23270 (NR_074193.1 and NR_041888.1) and DQ321746.1 of the well-known species Acidithiobacillus ferrooxidans were found, as well as two new wild strains of A. ferrooxidans. This result showed that the acidic remnant solution comprises a metapopulation. We assayed these strains to produce bioferric flocculant to enhance the subsequent pyrite bio-oxidation, applying two-stage chemical–bacterial oxidation. It was shown that the strains were already adapted to a high concentration of endogenous Fe2+ (up to 20 g·L−1), increasing the volumetric productivity of the bioferric flocculant. Thus, no preadaptation of the community was required. We detected Au and Ag particles originally occluded in the old pyritic flotation tailings assayed, but the extraction of Au and Ag by cyanidation resulted in ca. 30.5% Au and 57.9% Ag.

Response of physiological parameters in Dionaea muscipula J. Ellis teratomas transformed with rolB oncogene

Background Plant transformation with rol oncogenes derived from wild strains of Rhizobium rhizogenes is a popular biotechnology tool. Transformation effects depend on the type of rol gene, expression level, and the number of gene copies incorporated into the plant’s genomic DNA. Although rol oncogenes are known as inducers of plant secondary metabolism, little is known about the physiological response of plants subjected to transformation. Results In this study, the physiological consequences of rolB oncogene incorporation into the DNA of Dionaea muscipula J. Ellis was evaluated at the level of primary and secondary metabolism. Examination of the teratoma (transformed shoots) cultures of two different clones (K and L) showed two different strategies for dealing with the presence of the rolB gene. Clone K showed an increased ratio of free fatty acids to lipids, superoxide dismutase activity, synthesis of the oxidised form of glutathione, and total pool of glutathione and carotenoids, in comparison to non-transformed plants (control). Clone L was characterised by increased accumulation of malondialdehyde, proline, activity of superoxide dismutase and catalase, total pool of glutathione, ratio of reduced form of glutathione to oxidised form, and accumulation of selected phenolic acids. Moreover, clone L had an enhanced ratio of total triglycerides to lipids and accumulated saccharose, fructose, glucose, and tyrosine. Conclusions This study showed that plant transformation with the rolB oncogene derived from R. rhizogenes induces a pleiotropic effect in plant tissue after transformation. Examination of D. muscipula plant in the context of transformation with wild strains of R. rhizogenes can be a new source of knowledge about primary and secondary metabolites in transgenic organisms.

Cefuroxime-Loaded Hydrogels for Prevention and Treatment of Bacterial Contamination of Open Wounds

Dextran/Sulfodextran-graft-polyacrylamide- and polyacrylamide-based hydrogels were synthesized by radical polymerization and loaded with cefuroxime to obtain antimicrobial wound dressings. Antibiotic release from the antibiotic-loaded hydrogels into an aqueous solution was studied by the HPLC-UV method. It is shown that cefuroxime-loaded Dextran/Sulfodextran-graft-polyacrylamide hydrogels release the antibiotic more slowly compared to polyacrylamide hydrogel with the same density of cross-links. Antibacterial activity of the synthesized materials was tested in vitro against wild strains of S. aureus, E. coli, and Klebsiella spp. The possibility of using the obtained antimicrobial hydrogels for the treatment of infected wounds was confirmed in vivo in a rat model.

Exploitation of E. coli for the production of penicillin G amidase: a tool for the synthesis of semisynthetic β-lactam antibiotics

Background Penicillin G amidase/acylases from microbial sources is a unique enzyme that belongs to the N-terminal nucleophilic hydrolase structural superfamily. It catalyzes the selective hydrolysis of side chain amide/acyl bond of penicillins and cephalosporins whereas the labile amide/acyl bond in the β-lactam ring remains intact. Main body of abstract This review summarizes the production aspects of PGA from various microbial sources at optimized conditions. The minimal yield from wild strains has been extensively improved using varying strain improvement techniques like recombination and mutagenesis; further applied for the subsequent synthesis of 6-aminopenicillanic acid, which is an intermediate molecule for synthesis of a wide range of novel β-lactam antibiotics. Immobilization of PGA has also been attempted to enhance the durability of enzyme for the industrial purposes. Short conclusion The present review provides an emphasis on exploitation of E. coli to enhance the microbial production of PGA. The latest achievements in the production of recombinant enzymes have also been discussed. Besides E. coli, other potent microbial strains with PGA activity must be explored to enhance the yields. Graphical abstract

Comparison of Growth Performance of three Strains of Clarias gariepinus: Hybrid Strain, Selective Breeding Strain and Wild Strain Reared in Concrete Tanks

A comparative study was conducted to investigate the growth performance of three strains of Clarias gariepinus reared in concrete tanks. The experiment was carried out for the period of three weeks. Three strains of Clarias gariepinus which were compared were hybrid strain, selective breeding strain and the pure/wild strain. The experimental fish were randomly assigned to three experimental groups. Each treatment was therefore replicated three times with 60 fry per replicate in concrete tanks. At harvest there was no significant difference among Hybrid strain, Selective breeding strain and wild strain (P˃0.05) in fish’ final body weight (1.83±0.11, 1.178±0.46 and 1.739±0.42). The SGR for hybrid strain, selective breeding strain and wild strains were 12.93 ±0.23, 4.53±0.22and 12.81±0.26. The survival rate for hybrid strain, selective breeding strain and pure strain 70%, 80% and 66.66 %respectively. The was no significant difference (p˃0.05) in FCR (2.12±0.01, 2.12±0.03 and 2.11±0.01) for hybrid strain, selective breeding strain and wild strain respectively. Though the difference was not that significant the pure Clarias gariepinus had the lower FCR as compared to the others. Therefore, this study recommends that hybrid Clarias gariepinus has a good performance as compared to the selective breeding strain and the wild Clarias gariepinus.