Phytobacter diazotrophicus from Intestine of Caenorhabditis elegans Confers Colonization-Resistance against Bacillus nematocida Using Flagellin (FliC) as an Inhibition Factor

Symbiotic microorganisms in the intestinal tract can influence the general fitness of their hosts and contribute to protecting them against invading pathogens. In this study, we obtained isolate Phytobacter diazotrophicus SCO41 from the gut of free-living nematode Caenorhabditis elegans that displayed strong colonization-resistance against invading biocontrol bacterium Bacillus nematocida B16. The colonization-resistance phenotype was found to be mediated by a 37-kDa extracellular protein that was identified as flagellin (FliC). With the help of genome information, the fliC gene was cloned and heterologously expressed in E. coli. It could be shown that the B. nematocida B16 grows in chains rather than in planktonic form in the presence of FliC. Scanning Electronic Microscopy results showed that protein FliC-treated B16 bacterial cells are thinner and longer than normal cells. Localization experiments confirmed that the protein FliC is localized in both the cytoplasm and the cell membrane of B16 strain, in the latter especially at the position of cell division. ZDOCK analysis showed that FliC could bind with serine/threonine protein kinase, membrane protein insertase YidC and redox membrane protein CydB. It was inferred that FliC interferes with cell division of B. nematocidal B16, therefore inhibiting its colonization of C. elegans intestines in vivo. The isolation of P. diazotrophicus as part of the gut microbiome of C. elegans not only provides interesting insights about the lifestyle of this nitrogen-fixing bacterium, but also reveals how the composition of the natural gut microbiota of nematodes can affect biological control efforts by protecting the host from its natural enemies.

Amplificação isotérmica mediada por loop para detecção de patógenos de plantas

Disease control is crucial to minimize potential losses in agriculture and thereby maintain high crop yield. However, for its effectiveness, the pathogen must be detected early and correctly in the production fields. Different methods of diagnosis can be used, from those based on symptoms to molecular tests. Loop-mediated isothermal amplification (LAMP) is a molecular technique that has been widely used in several biological fields, due to the ease with which it can be applied. The reaction can be carried out in a single thermal condition, due to the use of Bst DNA polymerase, isolated from the bacterium Bacillus stearothermophilus, which has high displacement activity. LAMP is a highly exponential amplification method that produces the target DNA in amounts 109 -1010 times between 45 and 60 minutes at 60-65°C. Its advantages are the visualization of results directly with the naked eye and the fact that it does not need sophisticated equipment for its application. In phytopathology, the technique has been gaining prominence in the detection of fungi, viruses, bacteria, nematodes and phytoplasmas, as well as in the monitoring of fungicide-resistant fungi. LAMP can benefit agriculture so that early, accurate and sensitive diagnostics can be carried out in the fields of cultivation and minimize losses caused by diseases. In this review, we present and discuss LAMP tests, developed for plant pathogens detection, which can be useful for researchers who wish to use the technique in their research area

Isolation of Bacillus thuringiensis strains from Saudi Arabia soil and study of their potential efficiency against the lepidopteran pest Ephestia kuehniella

Insect pests represent a major threat to food crops and human health, and therefore have to be combated in several ways, including chemical methods. However, researchers demonstrated that these molecules are dangerous for the farmers, consumers and the environment in general. For this reason, scientists permanently searched environment friendly alternatives such as the use of the bacterium Bacillus thuringiensis classified as one of the best insect pathogens. This microorganism is known by its ability to produce two types of insecticidal proteins, Vegetative insecticidal proteins (Vip) and delta-endotoxins produced during vegetative and sporulation stages of growth, respectively. In the present study, 15 B. thuringiensis strains were isolated from soil collected from different regions in Saudi Arabia (Al Baha, Jeddah, Khulis and Yanbu). B. thuringiensis isolates were then classified according to the shape of their parasporal crystals identified under microscope and proteins content of these crystals. Delta-endotoxins efficiency of the different isolates was investigated and promising strains were identified as very active. After 5 days-treatment, B. thuringiensis isolates 14 and 7 killed Ephestia kuehniella larvae with low LC50 of about 59.18 and 65.67 mg/cm2, respectively. The results described in the present study proved that the new B. thuringiensis isolates could be of a great interest in the control of lepidopteran pests by using their delta-endotoxins in bioinsecticide formulations.

Biodegradation and Micro- Scale Treatability Pattern of Loblolly Pine Heartwood Bioincised by Bacillus Subtilis and Physisporinus Vitreus

One strategy for improving the treatability of refractory wood species is biological incising, and its efficiency depends on how the microorganisms modify the porous structure of the wood. Evaluation of the bioincised wood treatability on a micro-scale can thus help to better understand the treatability enhancing mechanisms. In the present study, the biodegradation pattern and micro-scale treatability of Loblolly pine (Pinus taeda L.) heartwood were determined after bioincising with the white-rot fungus Physisporinus vitreus (Pers.: Fr.) P. Karsten isolate 136 and bacterium Bacillus subtilis UTB22. Oven-dried specimens with dimensions of 50 mm × 25 mm × 15 mm (L × T × R) were incubated with the microorganisms at (23±2) °C and (65±5) % relative humidity for six weeks. The control and exposed wood blocks were then pressure treated by 1 % fluorescent dye (fluorescein)-containing water to study the treatability pattern under a fluorescence microscope. The longitudinal and tangential air permeability and compression strength parallel to the grain of the specimens were also determined at the end of the incubation period. Scanning electron microscopic (SEM) studies showed that degradation by B. subtilis UTB22 was limited to the pit membranes, but the cell walls were also degraded to some extent by P. vitreus. The fungus caused a higher mass loss compared to the bacterium, whereas the permeability enhancing ability of the bacterium was more pronounced. The fluorescent dye tracer also showed that higher treatability with more uniformity was obtained by B. subtilis UTB22. The improvement in treatability by both microorganisms was mainly due to the degradation of the earlywood tracheids.

Biodegradation Capacity and Activity Enzymatic of Bacillus subtilis against Low-Density Polyethylene

Aims: The objective of this work was to determine the degradation capacity of low-density polyethylene by the bacterium Bacillus subtilis and analyze the production of extracellular laccase activity. Methodology: The experiments was realized in 50 mL of culture medium, added with a fragment of known dry weight (1 cm2 colorless polyethylene bag squares), and were incubated at 28°C, pH 6.5, for 6 months under static conditions, determining the growth of the bacterium by dry weight (68, 75, and 91 mg), the production of extracellular protein (271, 234, and 326.1 mg/mL), and the degradation of the substrate by dry biodegraded (8.57%, 5.88%, and 11.76%). Results: The production of extracellular laccase enzyme was analyzed in presence of polyethylene, finding an enzymatic activity of laccase of 2.06, 1.49, and 2,03 U/mL, while in the control without substrate, no enzymatic activity was observed, which suggests that this enzyme may participate in the degradation of polyethylene. In addition, some characteristics of the extracellular enzymatic activities were analyzed, such as stability at 4oC and 28oC, optimal pH and temperature, the effect of protein and substrate concentration. Conclusion: The extracellular protein production and dry weight of the bacterium are higher in the presence of low-density polyethylene. The laccase activity is very stable at 4oC and 28oC, the most effective pH and temperature, were 4.5 and 28oC, and present an incubation time of 5 minutes, and this data suggest that this enzymatic activitiy may participate in the degradation of low density polyethylene.