Ralstonia solanacearum is a rod-shaped phytopathogenic bacterium that causes lethal wilt disease in many plants. On solid agar growth medium, in the early hour of the growth of the bacterial colony, the type IV pili-mediated twitching motility, which is important for its virulence and biofilm formation, is prominently observed under the microscope. In this study, we have done a detailed observation of twitching motility in R. solanacearum colony. In the beginning, twitching motility in microcolonies was observed as a density-dependent phenomenon that influences the shape and sizes of the microcolonies. No such phenomenon was observed in Escherichia coli, where twitching motility is absent. In the early phase of colony growth, twitching motility exhibited by the cells at the peripheral region of the colony was more prominent than the cells towards the centre of the colony. Using a time scale photography and merging those into a video, twitching motility was observed as an intermittent phenomenon that progresses in layers in all directions as finger-like projections at the peripheral region of a bacterial colony. Each layer of bacteria twitches on top of the other and produces a multi-layered film-like appearance. We found that the duration between the emergence of each layer diminishes progressively as the colony becomes older. This study on twitching motility demonstrates distinctly heterogeneity among the cells within a colony regarding their dynamics and the influence of microcolonies on each other regarding colony shape and size.
In the current investigation, a macrofungus was collected from Quaid-i-Azam University Islamabad. The collected fungus was identified as Ganoderma multipileum, and further exploited for the synthesis of nanoparticles using zinc metals. Chemical and morphological characterization of synthetized nanoparticles was through Fourier Transfer InfraRed spectroscopy analysis (FTIR), X-ray diffraction analysis (XRD), Energy dispersive X-ray analysis (EDX), Scanning Electron Microscopy analysis (SEM) and UV-Vis spectrum showed a broad absorption between 350 and 380 nm, which indicates the synthesis of ZnO NPs. ZnONPs have been used in a variety of biomedical studies including such as biocompatibility, antifungal, antileishmanial, and antibacterial studies. abilities, antifungal, antileishmanial, and antibacterial studies. The ZnO nanoparticles showed a strong antibacterial effect against gram-positive (Klesbsilla pneumonia and Staphylococcus aureus) and gram-negative (Eschericia coli and Pseudomonas aeruginosa) bacteria. Furthermore, the ZnO nanoparticles also showed a high antifungal effect against different fungus. The current study concludes that Ganoderma multipileum works as a novel and eco-friendly source for the synthesis of ZnO NPs with prominent biological application that can be further applied in different fields.
Indiscriminate use of antibiotics has led to the emergence of antibiotic resistant microbes and the loss of natural flora in aquaculture systems ultimately necessitating the ban of many of the chemotherapeutants in aquaculture. Actinobacteria play a profound role in the biogeochemical cycling in the marine environment and they represent the principal source of secondary metabolites with antimicrobial property. In the present study, 98 marine derived actinomycete isolates were screened for antimicrobial activity against the common aquatic pathogens. A potent actinomycete isolate S26, identified as Streptomyces variabilis based on 16S rRNA gene sequencing was used for further study. Optimization of the fermentation medium for secondary metabolite production was carried out by response surface methodology (RSM) using DESIGN EXPERT. The ANOVA of the quadratic regression model demonstrated that the model was highly significant for the response concerned i.e., antimicrobial activity as evident from the Fisher’s F- test with a very low probability value [(P model>F) = 0.0001]. Of the 10 different solutions suggested by the software, the most suitable composition was found to be starch, 1.38 %; soy powder, 0.88 %; ammonium sulphate, 0.16 % and salinity, 27.76 ‰. S. variabilis S26 cultured in the optimized production medium was applied in the Penaeus monodon larval rearing system and the total Vibrio count and survival rate were estimated. S. variabilis S26 treatment showed a significant reduction in Vibrios and better survival in the Penaeus monodon culture system compared to the control.
The increasing growth of agro-industrial activity resulting in excessive amounts of agri-waste has led to the accumulation of a large quantity of lignocellulosic residues all over the world, in particular, deforestation initiatives for the removal of invasive trees in South Africa. These lignocellulosic residues are rich in energy resources consisting of a mixture of natural polymers based on lignin, cellulose and hemicellulose. The use of lignolytic fungi such as mushrooms in solid-state fermentation could sufficiently degrade the indigestible lignocellulosic components and add medicinal and nutritional value to otherwise unusable, high-energy waste material. The digestive type of animal for which the potential feed is developed must be identified and considered before deciding on the bioconversion method and process, since the outcomes for obtaining potentially high-quality feeds for non-ruminant and ruminant animals are different. The current study presents the data of the bioconversion of lignocellulosic substrate using solid-state fermentation with the edible and medicinal mushrooms, Ganoderma lucidum, Pleurotus ostreatus, and a possible new species, to increase digestibility and nutritional value to be applied as ruminant animal feed. The solid-state fermentation process was optimised and the resulting product analysed for the degradation of the lignocellulosic components. Results indicated that the solid-state fermentation duration and mushroom species were key components in achieving significant degradation. Data obtained after 18 weeks of degradation indicated a significant (p < 0.05) reduction in the acid detergent fibre, acid detergent lignin and neutral detergent fibre fractions of the biomass, with up to 20% reduction in indigestible components.
An underutilized experimental design was used to isolate adapted mutants of the model bacterium Pseudomonas putida KT2440. The experimental design consisted of subjecting a random pool of mini-Tn5 mutants of P. putida KT2440 to several rounds of selection in the rhizosphere of soybean irrigated with NaCl solution. Isolated adapted mutants (MutAd) showed a mutation in a gene encoding the membrane-binding protein LapA, which is involved in the early stages of biofilm formation on abiotic surfaces. Two MutAd bacteria (MutAd160 and MutAd185) and a lapA deletion mutant were tested to study the effect of this gene on salt tolerance, rhizosphere fitness, extracellular polymeric substances (EPS) production, and plant growth promotion. The inability of the mutants to form biofilm did not hinder attachment to soybean seeds and roots. MutAd bacteria showed an overproduction of EPS when grown under saline conditions, which would compensate for the lack of biofilm formation. MutAd185 bacteria showed increased root attachment and growth promotion of soybean in slightly saline soils. The proposed experimental design would be useful to accelerate bacterial adaptation to the rhizosphere of plants under a given environmental condition, identify genetic mutations that benefit bacterial fitness in that condition, and thus increase their ability to promote plant growth.
Aflatoxin and other mycotoxin contamination are major threats to global food security and present an urgent need to secure the global food crop against spoilage by mycotoxigenic fungi. Cocoa material is noted for naturally low aflatoxin contamination. This study was designed to assess the potential for harnessing cocoa-associated filamentous fungi for the biocontrol of aflatoxigenic Aspergillus flavus. The candidate fungi were isolated from fermented cocoa beans collected from four cocoa-growing areas in Ghana. Molecular characterization included ITS-sequencing for identification and PCR to determine mating type. Effects of the candidate isolates on growth and aflatoxin-production by an aflatoxigenic A. flavus isolate (BANGA1) were assessed. Aflatoxin production was monitored by UV fluorescence and quantified by ELISA. Thirty-six filamentous fungi were cultured and identified as Aspergillus, Cladosporium, Lichtheimia or Trichoderma spp. isolates. The isolates generally interacted negatively with BANGA1 growth and aflatoxin production. The A. niger and A. aculeatus biocontrol candidates showed the strongest colony antagonism (54–94%) and reduction in aflatoxin production (12–50%) on agar. In broth, the A. niger isolates reduced aflatoxin production by up to 97%. Metabolites from the A. niger isolates showed the strongest inhibition of growth by BANGA1 and inhibited aflatoxin production. Four of the candidate isolates belonged to the MAT1-1 mating type and 12 identified as MAT1-2. This may be indicative of the potential for genetic recombination events between fungi in the field, and finding which is particularly relevant to the risk posed by A. flavus biocontrol measures that rely on atoxigenic A. flavus strains.
Background Plant mediated induced systemic resistance against the plant-parasitic nematode, M. incognita infecting tomato cv Pusa Ruby was evaluated on application of four nematicidal rhizobacterial isolates (Bacillus subtilis, B. pumilus, B. megaterium and B. cereus) as elicitors and compared with the application of a chemical nematicide, Velum Prime. Methods The bioefficacy trial was conducted in pots preinoculated with the above isolates followed by M. incognita inoculation tomato to observe the reduction in nematode infection at 60 days and effect on photosynthetic and transpiration rates. The mechanism of induced resistance was assessed using qRT-PCR for quantification of three key defense genes(PR-1b, JERF3 and CAT) at 0,2,4,8 and 16 days after inoculation (DAI). The defense enzymes viz., super oxide dismutase(SOD), polyphenol oxidase(PPO), peroxidase (PO), and phenylalanine ammonia lyase (PAL) were quantified. Results Significant reduction in per cent root galling viz. 84.21 in B. pumilus, 83.70 in B. megaterium, 91.95 in B. subtilis, 81.8 in B. cereus, was observed compared to control. The reproduction factor was the lowest (15.83) in B. subtilis, followed by B. pumilus (21.00), compared to 48.16 in control, with enhanced photosynthetic and transpiration rate. The defense genes, PR-1b, JERF3 and CAT were expressed at 2.5 to 7.5 folds in rhizobacterial treated plants, but not in Velum Prime treatment. The increase in enzyme levels (μmol/min/mg) for SOD was from 1.5 to 17.5, PPO from 2.1 to 7.8, PO from 1.8 to 10.2, and PAL from 1.8 to 8.7 during 0 to 16 DAI.
The 3,4-dihydroxyphenylalanine (DOPA) melanin is one of important virulence factors for Cryptococcus neoformans, which may trigger immune responses in the host. It is worth exploring the genetic function of C. neoformans, by which we may derive more antifungal strategies. Therefore, we established two systems that were constructed quickly and easily for the knock-down/knock-out of LAC1 gene: RNA interference (RNAi) and clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9. The RNAi system used pSilencer 4.1-CMV neo plasmid and short hairpin RNA to realize the effective transcriptional suppression. The CRISPR-Cas9 system used the PNK003 vectors to obtain a stable albino mutant strain. The results of phenotype, qRT-PCR, Transmission Electron Microscope (TEM) and spectrophotometry were used to assess the ability of melanin production. As a result, the RNAi system displayed attenuation of transcriptional suppression when the transformants continuously passed on new plates. However, the transcriptional suppression of long loop in short hairpin RNA were more powerful and lasted longer. The CRISPR-Cas9 system constructed an albino strain completely without the ability to produce melanin. Considering the weakening of transcriptional suppression, we recommend using a long loop for the RNAi system and 1st or 2nd passage of knockdown strains for the subsequent studies. Besides, the different capacities of melanin production might be useful for exploring the linear relation between melanin and immunoreaction of the host. In addition, we recommend applying the PNK003 vectors to other serotypes of C. neoformans for quick screening of possible trait-regulating genes because of its easy construction and valid knockout effect.