Influence of bacteria on the maintenance of a yeast during Drosophila melanogaster metamorphosis

Interactions between microorganisms associated with metazoan hosts are emerging as key features of symbiotic systems. Little is known about the role of such interactions on the maintenance of host-microorganism association throughout the host’s life cycle. We studied the influence of extracellular bacteria on the maintenance of a wild isolate of the yeast Saccharomyces cerevisiae through metamorphosis of the fly Drosophila melanogaster reared in fruit. Yeasts maintained through metamorphosis only when larvae were associated with extracellular bacteria isolated from D. melanogaster faeces. One of these isolates, an Enterobacteriaceae, favoured yeast maintenance during metamorphosis. Such bacterial influence on host-yeast association may have consequences for the ecology and evolution of insect-yeast-bacteria symbioses in the wild.

Pathogenic and biological characterisation of T-DNA insertional mutants of a Colletotrichum gloeosporioides casual organism of apple anthracnose

Anthracnose leaf spot caused by Colletotrichum gloeosporioides is an important disease of apples, resulting in serious damage to the fruit production. In this paper, the pathogenic and physiological characters of sixteen isolates and the wild isolate “Stj16” were studied. In the current study, we generated C. gloeosporioides strains expressing green fluorescence by introducing a GFP gene via an Agrobacterium tumefaciens-mediated transformation (ATMT). To confirm the subcellular localisation of the A2799 gene, an A2799gfp fusion expression mutant was constructed. After observation of the fusion expression, the A2799gfp fusion expression protein was located in the peroxisomes of the cell. The pathogenicity results showed that the mutants A4204, M44, A1919, A3638 and A1598 lost the pathogenic capability and virulence, however, the virulence of the mutants A1764, A439, A3885, G1183, A3144, A1649 and A2675 increased significantly to the apple fruits compared to the wild isolate “Stj16”. The biological study indicated that a Rose Bengal Agar (RBA) medium decreased the mycelium growth, but it can increase the sporulation for most of the isolates. The mutant A4204 does not grow well at pH 4.0 and pH 8.0, and mutant M44 just has the optimum growth at pH 8.0, and a 12 h light and 12 h dark condition stimulates the sporulation for most of the tested mutants, but the A1764 mutant more sporulated at regular dark conditions. All the mutants and “Stj16” grew vigorously at 25 °C–30 °C, for “Stj16”, it produced the highest number of conidia at 30 °C compared with the other temperatures. Based on the biological study, we found the best growing and sporulation conditions for all the tested isolates. The information generated in the present study will facilitate molecular research on this devastating fungus.

Aerobic growth physiology of Saccharomyces cerevisiae on sucrose is strain-dependent

ABSTRACT Present knowledge on the quantitative aerobic physiology of the yeast Saccharomyces cerevisiae during growth on sucrose as sole carbon and energy source is limited to either adapted cells or to the model laboratory strain CEN.PK113-7D. To broaden our understanding of this matter and open novel opportunities for sucrose-based biotechnological processes, we characterized three strains, with distinct backgrounds, during aerobic batch bioreactor cultivations. Our results reveal that sucrose metabolism in S. cerevisiae is a strain-specific trait. Each strain displayed distinct extracellular hexose concentrations and invertase activity profiles. Especially, the inferior maximum specific growth rate (0.21 h-1) of the CEN.PK113-7D strain, with respect to that of strains UFMG-CM-Y259 (0.37 h-1) and JP1 (0.32 h-1), could be associated to its low invertase activity (0.04–0.09 U/mgDM). Moreover, comparative experiments with glucose or fructose alone, or in combination, suggest mixed mechanisms of sucrose utilization by the industrial strain JP1, and points out the remarkable ability of the wild isolate UFMG-CM-259 to grow faster on sucrose than on glucose in a well-controlled cultivation system. This work hints to a series of metabolic traits that can be exploited to increase sucrose catabolic rates and bioprocess efficiency.

Aerobic growth physiology of Saccharomyces cerevisiae on sucrose is strain-dependent

Present knowledge on the quantitative aerobic physiology of the yeast Saccharomyces cerevisiae during growth on sucrose as sole carbon and energy source is limited to either adapted cells or to the model laboratory strain CEN.PK113-7D. To broaden our understanding of this matter and open novel opportunities for sucrose-based biotechnological processes, we characterized three strains, with distinct backgrounds, during aerobic batch bioreactor cultivations. Our results reveal that sucrose metabolism in S. cerevisiae is a strain-specific trait. Each strain displayed a distinct extracellular hexose concentration and invertase activity profiles. Especially, the inferior maximum specific growth rate (0.21 h−1) of the CEN.PK113-7D strain, with respect to that of strains UFMG-CM-Y259 (0.37 h−1) and JP1 (0.32 h−1), could be associated to its low invertase activity (0.04 to 0.09 U mgDM−1). Moreover, comparative experiments with glucose or fructose alone, or in combination, suggest mixed mechanisms of sucrose utilization by the industrial strain JP1, and points out the remarkable ability of the wild isolate UFMG-CM-259 to grow faster on sucrose than on glucose in a well-controlled cultivation system. This work hints to a series of metabolic traits that can be exploited to increase sucrose catabolic rates and bioprocess efficiency.Abstract Figure

Comparison of Yield, Nutrient Content and Antibacterial Activities of Wild and Cultivated Isolates of Pleurotus djamor

Background: Pleurotus species constitutes one of the choicest edible mushrooms, it is commonly known as “Oyster Mushroom” and in India it is commonly called as “Dhingri. It has important medicinal, biotechnological properties and environmental applications. Its cultivation can be done on a number of agricultural wastes and organic waste materials. There are significant problems in classifying Pleurotus isolates using only morphological characters which are often unreliable and inconclusive mainly due to the large influence exerted by environmental factors. Methods: A wild isolate of Pleurotus was collected from North western Himalayas and its identity was confirmed by molecular studies. Yield, nutritional components and its bioactive molecules were compared with the cultivated isolate of Pleurotus djamore Antibacterial activities of both the isolates of were performed against Escherichia coli and Staphylococcus aureus by disc diffusion. Results: Molecular studies confirmed the identity of wild isolate of Pleurotus as Pleurotus djamore. The maximum yield of wild isolate was on paddy straw followed by wheat straw. The protein content was 32.3±0.50g-1 in wild isolate and 28.7±1.67g-1 in cultivated isolate. Presence of nutritional components and phytochemicals inferred in this study indicate the importance of Pleurotus djamore in the pharmaceutical.

Caenorhabditis elegans nematodes are not attracted to the terrestrial isopod Porcellio scaber

ABSTRACTPhoresy is a behavior in which an organism, the phoront, travels from one location to another by ‘hitching a ride’ on the body of a host as it disperses. Some phoronts are generalists, taking advantage of any available host. Others are specialists and travel only when specific hosts are located using chemical cues to identify and move (chemotax) toward the preferred host. Free-living nematodes, like Caenorhabditis elegans, are often found in natural environments that contain terrestrial isopods and other invertebrates. Additionally, the C. elegans wild strain PB306 was isolated associated with the isopod Porcellio scaber. However, it is currently unclear if C. elegans is a phoront of terrestrial isopods, and if so, whether it is a specialist, generalist, or developmental stage-specific combination of both strategies. Because the relevant chemical stimuli might be secreted compounds or volatile odorants, we used different types of chemotaxis assays across diverse extractions of compounds or odorants to test whether C. elegans is attracted to P. scaber. We show that two different strains – the wild isolate PB306 and the laboratory-adapted strain N2 – are not attracted to P. scaber during either the dauer or adult life stages. Our results indicate that C. elegans was not attracted to chemical compounds or volatile odorants from P. scaber, providing valuable empirical evidence to suggest that any associations between these two species are likely opportunistic rather than specific phoresy.

Susceptibility of Spodoptera frugiperda and Chrysodeixis includens (Lepidoptera: Noctuidae) to infections caused by Metarhizium rileyi

ABSTRACT Due to the reduced host spectrum of the entomopathogenic fungus Metarhizium rileyi, its pathogenicity against different target insects must be assessed to develop biopesticides capable of controlling more than one pest species. This study aimed to evaluate the susceptibility of the pest species Chrysodeixis includens and Spodoptera frugiperda to different isolates of M. rileyi and, thus, determine a possible influence of the host of origin on the pathogenic activity of these isolates. Three isolates [CG1312 (C. includens as original host), CG381 (S. frugiperda as original host) and a new wild isolate (C. includens as original host)] were tested against larvae of C. includens and S. frugiperda, in third instar age, by treatment of surfaces with conidial suspension, under laboratory conditions. Both species were susceptible to the isolates of M. rileyi, with mortality rates of 53-58 % for C. includens and 74-84 % for S. frugiperda. The results suggest that the host of origin may not be determinant in the selection of pathogenic isolates of M. rileyi against these two pest insects.

Natural diversity in the predatory behavior facilitates the establishment of a new robust model strain for nematode-trapping fungi

Nematode-trapping fungi (NTF) are a group of specialized microbial predators that consume nematodes when food sources are limited. Predation is initiated when conserved nematode ascaroside pheromones are sensed, followed by the development of complex trapping devices. To gain insights into the co-evolution of this inter-kingdom predator-prey relationship, we investigated natural populations of nematodes and NTF, that we found to be ubiquitous in soils. Arthrobotrys species were sympatric with various nematode species and behaved as generalist predators. The ability to sense prey amongst wild isolates of A. oligospora varied greatly, as determined by the number of traps after exposure to Caenorhabditis elegans. While some strains were highly sensitive to C. elegans and the nematode pheromone ascarosides, others responded only weakly. Furthermore, strains that were highly sensitive to the nematode prey also developed traps faster. The polymorphic nature of trap formation correlated with competency in prey killing, as well as with the phylogeny of A. oligospora natural strains, calculated after assembly and annotation of the genomes of twenty isolates. A chromosome level genome assembly and annotation was established for one of the most sensitive wild isolate, and deletion of the only G protein β subunit-encoding gene of A. oligospora nearly abolished trap formation, implicating G protein signaling in predation. In summary, our study establishes a highly responsive A. oligospora wild isolate as a novel model strain for the study of fungal-nematode interactions and demonstrates that trap formation is a fitness character in generalist predators of the NTF family.Significance statementNematode-trapping fungi (NTF) are carnivorous microbes that hold potential to be used as biological control agents due to their ability to consume nematodes. In this work we show that NTF are ubiquitous generalist predators found in sympatry with their prey in soil samples. Wild isolates of NTF displayed a naturally diverse ability to execute their predatory lifestyle. We generated a large whole genome sequencing dataset for many of the fungal isolates that will serve as the basis of future projects isolates. In particular, we establish TWF154, a highly responsive strain of Arthrobotrys oligospora, as a model strain to study the genetics of NTF. Lastly, we provide evidence that G-protein signaling is necessary for trap induction in NTF.

Phototaxis in a wild isolate of the cyanobacterium Synechococcus elongatus

Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed “phototaxis,” enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium Synechocystis sp. strain PCC 6803, but the rod-shaped Synechococcus elongatus PCC 7942, studied for circadian rhythms and metabolic engineering, has no phototactic motility. In this study we report a recent environmental isolate of S. elongatus, the strain UTEX 3055, whose genome is 98.5% identical to that of PCC 7942 but which is motile and phototactic. A six-gene operon encoding chemotaxis-like proteins was confirmed to be involved in phototaxis. Environmental light signals are perceived by a cyanobacteriochrome, PixJSe (Synpcc7942_0858), which carries five GAF domains that are responsive to blue/green light and resemble those of PixJ from Synechocystis. Plate-based phototaxis assays indicate that UTEX 3055 uses PixJSe to sense blue and green light. Mutation of conserved functional cysteine residues in different GAF domains indicates that PixJSe controls both positive and negative phototaxis, in contrast to the multiple proteins that are employed for implementing bidirectional phototaxis in Synechocystis.