Competition on Using Nutrient for Growth between Bacillus spp. and Vibrio harveyi

ABSTRACT Competition, by using nutrient for growth, between Bacillus pumilus NW01, B. sphaericus NW02 and B. subtilis NW03 and Vibrio harveyi in vitro was studied by culturing each bacteria in Nutrient Broth (+ 1.5% NaCl). The initial concentration of 10 2 CFU/ml in monoculture and co-culture of Bacillus spp. and V. harveyi was used. Total Bacillus and Vibrio counts were conducted after 0, 24, 48, 72, 96 and 120 hours. B. pumilus NW01, B. sphaericus NW02 and B. subtilis NW03 decreased V. harveyi by 39.10, 43.62 and 34.46%, respectively. Antagonistic properties of Bacillus spp. against V. harveyi in vivo was tested by feeding shrimp with spores (10 11 -10 12 CFU/g) of each Bacillus and their mixture at 5 g/kg for 1 month. The amount of Vibrio spp. in the intestine of all Bacillus treated shrimp decreased by 20.97-32.45 % as compared with the control. The results showed that these Bacillus spp. could be applied as an effective probiotic in Penaeus monodon culture

Impact of neonicotinoid seed treatment of cotton on the cotton leafhopper, Amrasca devastans(Hemiptera: Cicadellidae), and its natural enemies

BACKGROUND Neonicotinoid seed treatments suppress populations of pest insects efficiently and can enhance crop growth, but they may have negative effects on beneficial arthropods. We evaluated the effects of either imidacloprid or thiamethoxam on the abundances of a sucking pest, the cotton leafhopper (Amrasca devastans), and its arthropod predators under field conditions. We also evaluated the impact of seed treatment on transgenic cotton plant growth, with pests and natural enemies present or absent. RESULTS Imidacloprid and thiamethoxam reduced pest abundance, with greater effects when dosages were higher. Treatment at recommended doses delayed the pest in reaching the economic damage threshold by around 10–15 days (thiamethoxam) and 20 days (imidacloprid). Recommended doses also enhanced plant growth under all tested conditions; growth is affected directly as well as via pest suppression. Neonicotinoid applications reduced abundance of beneficial arthropods, with lower populations after higher doses, but negative effects of imidacloprid were not apparent unless the manufacturer-recommended dose was exceeded. CONCLUSION Imidacloprid applied at the recommended dose of 5 g kg−1 seed is effective against A. devastans and appears to be safer than thiamethoxam for natural enemies, and also enhances plant growth directly. We caution, however, that possible sublethal negative effects on individual beneficial arthropods were not evaluated

Observation of Live Ticks (Haemaphysalis flava) by Scanning Electron Microscopy under High Vacuum Pressure

Scanning electron microscopes (SEM), which image sample surfaces by scanning with an electron beam, are widely used for steric observations of resting samples in basic and applied biology. Various conventional methods exist for SEM sample preparation. However, conventional SEM is not a good tool to observe living organisms because of the associated exposure to high vacuum pressure and electron beam radiation. Here we attempted SEM observations of live ticks. During 1.5×10−3 Pa vacuum pressure and electron beam irradiation with accelerated voltages (2–5 kV), many ticks remained alive and moved their legs. After 30-min observation, we removed the ticks from the SEM stage; they could walk actively under atmospheric pressure. When we tested 20 ticks (8 female adults and 12 nymphs), they survived for two days after SEM observation. These results indicate the resistance of ticks against SEM observation. Our second survival test showed that the electron beam, not vacuum conditions, results in tick death. Moreover, we describe the reaction of their legs to electron beam exposure. These findings open the new possibility of SEM observation of living organisms and showed the resistance of living ticks to vacuum condition in SEM. These data also indicate, for the first time, the usefulness of tick as a model system for biology under extreme condition

The Role of the Proteinase Inhibitor Ovorubin in Apple Snail Eggs Resembles Plant Embryo Defense against Predation

BACKGROUND: Fieldwork has thoroughly established that most eggs are intensely predated. Among the few exceptions are the aerial egg clutches from the aquatic snail Pomacea canaliculata which have virtually no predators. Its defenses are advertised by the pigmented ovorubin perivitellin providing a conspicuous reddish coloration. The nature of the defense however, was not clear, except for a screening for defenses that identified a neurotoxic perivitellin with lethal effect on rodents. Ovorubin is a proteinase inhibitor (PI) whose role to protect against pathogens was taken for granted, according to the prevailing assumption. Through biochemical, biophysical and feeding experiments we studied the proteinase inhibitor function of ovorubin in egg defenses. METHODOLOGY/PRINCIPAL FINDINGS: Mass spectrometry sequencing indicated ovorubin belongs to the Kunitz-type serine proteinase inhibitor family. It specifically binds trypsin as determined by small angle X-ray scattering (SAXS) and cross-linking studies but, in contrast to the classical assumption, it does not prevent bacterial growth. Ovorubin was found extremely resistant to in vitro gastrointestinal proteolysis. Moreover feeding studies showed that ovorubin ingestion diminishes growth rate in rats indicating that this highly stable PI is capable of surviving passage through the gastrointestinal tract in a biologically active form. CONCLUSIONS: To our knowledge, this is the first direct evidence of the interaction of an egg PI with a digestive protease of potential predators, limiting predator's ability to digest egg nutrients. This role has not been reported in the animal kingdom but it is similar to plant defenses against herbivory. Further, this would be the only defense model with no trade-offs between conspicuousness and noxiousness by encoding into the same molecule both the aposematic warning signal and an antinutritive/antidigestive defense. These defenses, combined with a neurotoxin and probably unpalatable factors would explain the near absence of predators, opening new perspectives in the study of the evolution and ecology of egg defensive strategies

Breeding for increased nitrogen-use efficiency: a review for wheat (T. aestivum L.)

Nitrogen fertilizer is the most used nutrient source in modern agriculture and represents significant environmental and production costs. In the meantime, the demand for grain increases and production per area has to increase as new cultivated areas are scarce. In this context, breeding for an efficient use of nitrogen became a major objective. In wheat, nitrogen is required to maintain a photosynthetically active canopy ensuring grain yield and to produce grain storage proteins that are generally needed to maintain a high end-use quality. This review presents current knowledge of physiological, metabolic and genetic factors influencing nitrogen uptake and utilization in the context of different nitrogen management systems. This includes the role of root system and its interactions with microorganisms, nitrate assimilation and its relationship with photosynthesis as postanthesis remobilization and nitrogen partitioning. Regarding nitrogen-use efficiency complexity, several physiological avenues for increasing it were discussed and their phenotyping methods were reviewed. Phenotypic and molecular breeding strategies were also reviewed and discussed regarding nitrogen regimes and genetic diversity

Molecular interactions between wheat and Pseudomonas fluorescens role of DAPG and type III secretion on early changes in root gene expression

The antifungal metabolite 2,4-diacetylphloroglucinol (DAPG) is produced by certain fluorescent Pseudomonas spp. and is capable of functioning as a microbe associated molecular pattern (MAMP) or factor that triggers the plant immune response to foliar pathogens. In Triticum aestivum L. (wheat), the root-colonizing bacterium Pseudomonas fluorescens strain Q8r1-96 modulates multiple stress pathways in wheat roots and is known to play a role in biological control. Strain Q8r1-96 is a DAPG producer that colonizes wheat roots rapidly and maintains its populations on roots over a sustained period. Much is known about the role of DAPG in induced systemic resistance (ISR) (foliar response) but not much is known about localized root responses at the molecular level. To study the molecular mechanisms underlying this triggered immunity in wheat roots, two wheat cultivars, Buchanan and Tara, were selected because they differentially support rhizoplane DAPG accumulation. In Chapter 1, I tested the hypothesis that DAPG is important for localized root defense responses, therefore, a DAPG mutant of Q8r1-96 should differ from the wild type in induction of root gene expression. The functional type III secretion system (T3SS) of Q8r1-96 was shown to inhibit PAMP triggered immunity (PTI) responses on tobacco leaves; however, the responses of wheat root genes remain unknown. In Chapter 2, I tested the hypothesis that localized roots defense responses are governed by bacterial effectors introduced into the host by the T3SS. The results showed that DAPG and T3SS are not key factors for inducing targeted defense/stress responses in wheat roots. Moreover, our findings revealed a cultivar-dependent response to all three strains of bacteria including Q8r1-96, 4C5, and PST