Investigation of insect dynamics on flowering of Irvingia gabonensis trees in southern Nigeria: towards indigenous agroforestry tree crop development for food security

Irvingiaga bonensis (O’Rorke) Baill., is an indigenous fruit tree species of high economic importance in the forest zone of West and Central Africa. In Nigeria, it is known to have high potentials for contribution to the food security and viable food value chain. This study investigated the guilds of insect visitors to the tree species in southern Nigeria (Enugu and Ibadan) through use of fly traps for collection of insect specimens. Proper identification of the insects and determination of other parameters such as the number of days and time of visits across two sites were carried out based on observations. In addition, relative frequency of visits, across the tree crown strata were also compared. Analysis of variance on the various parameters showed that the number of days of visit and the three periods of the day were significantly different respectively at 5 % level of probability. The study also showed that there were homogenous insect populations in southern Nigeria, thus contributing information to the breeding potentials of the species. The insect order Hymenoptera appeared most prevalent of all insect order populations in this investigation. Pollinating agents, if known, will contribute to the breeder’s choice in carrying out trials on indigenous species like I. gabonensis, which is being recommended for further and improved cultivation trials towards adding to the food security and food value chain in Nigeria.Keywords: Flowering, Irvingia gabonensis, indigenous economic tree, insect classification, visitation frequenc

The physiological response of the white-rot fungus, Schizophyllum commune to Trichoderma Viride, during interspecific mycelial combat

Fungal species compete for space and nutrients in organic matter, resulting in strong morphological and biochemical reactions in the interacting mycelia. Interspecific mycelial interactions have attracted extensive studies because of their potential applications in biological control, bio-pulping, screening for novel bioactive metabolites and enhancement of extracellular enzyme production. Studies of interspecific mycelial combat have also contributed to the understanding of the structure and development of fungal communities. Although the behaviour of interacting mycelia has been understood, mainly at the morphological level, the biochemical aspects have yet to be fully elucidated. The main aim of this study was to endeavour to understand the underlying cellular and molecular response patterns and adaptations of the white-rot fungus, Schizophyllum commune to a highly antagonistic strain of Trichoderma viride, by correlating the expression patterns of metabolites, proteins and selected genes of Schizophyllum commune in response to the antagonist. The study also investigated the implication of oxidative damage in these response patterns. Microscopic examination of stained and unstained mycelia of S. commune confronted by the mycelia of T. viride, revealed cell wall lysis, protoplasmic degeneration, hyphal expansion and subsequent hyphal disintegration, hence, cell death in the mycelia of S. commune, after 7 days of mycelial contact. Metabolite patterns of both species near the interaction zone were profiled by HPLC and GC/MS, in comparison to their self-paired mycelia. Sugar alcohols, phenolic compounds and organic acids were up-regulated in the interacting mycelia of both species, while �-aminobutyric acid, myo-inositol phosphate, pyridoxine and N-acetylglucosamine, were up-regulated in S. commune mycelia with a concurrent decrease in the levels of fatty acids detected in the latter. Expression patterns of selected genes of S. commune confronted by T. viride were investigated by RT-PCR, relative to patterns in its self-paired cultures. Genes encoding proteins involved in the synthesis of cell wall polymers, protein synthesis and protein quality control, signalling, and stress response were up-regulated. On the other hand, genes that code for proteins associated with glycolysis, nitrogen assimilation, membrane transport, mitochondrial ATP-synthetic machinery, and cellular multiplication/growth were down-regulated. Changes in protein expression were profiled in the mycelia of both species paired against each other using 2- Dimensional gel electrophoresis, and differentially expressed proteins were identified by MALDI-TOF-MS/MS, following peptide fragmentation. Proteins involved in protein synthesis and assembly, unfolded protein response, response to cellular injury, synthesis of phenolic compounds, recycling of carbon and nitrogen were up-regulated in the confronted mycelial domain of S. commune. Proteins involved in glycolysis and heat shock response were predominantly down-regulated in the mycelia of S. commune paired against T. viride. Proteins associated with antagonism, cellular metabolism, glycolysis, and ATP generation and protein synthesis were up-regulated in the mycelia of T. viride interacting with S. commune with a decline in the detected levels of proteins involved in cytoskeleton organisation. Biochemical assays revealed increases in the activity levels of antioxidant enzymes, superoxide dismutase, catalase, succinic semialdehyde dehydrogenase, glucose-6-phosphate dehydrogenase and in the levels of indicators of oxidative stress and secondary metabolism, such as lipid peroxidation, protein carbonylation, superoxide anion and phenolic levels in the mycelia of S. commune paired against T. viride. Similarly, the activities and protein levels of phenol-oxidising enzymes, namely laccase and manganese peroxidase increased in the confronted mycelial domain of S. commune. Chitinase activity increased in mixed liquid cultures of both fungi. Protein, and gene expression patterns, in the confronted mycelia of S. commune suggest an increase in the flux through the protein synthetic machinery, possibly resulting in endoplasmic reticulum stress, which may have activated the unfolded protein response. These are strong indications of oxidative stress induction and switch of mycelial growth to secondary metabolism. There was little evidence of antagonism by S. commune towards T. viride, suggesting that the patterns reported herein, may be a response rather than an attack mechanism towards the latter

Prevalence, distribution and antimicrobial susceptibility pattern of bacterial isolates from a tertiary Hospital in Malawi

Background: Bacterial infections are a significant cause of sickness and death in sub-Saharan Africa. This study aimed at establishing the prevalence, distribution and antimicrobial susceptibility pattern of major bacterial isolates from patients accessing medical care at a tertiary hospital in Malawi. Methods: We retrospectively reviewed bacteria culture and antimicrobial susceptibility records for 4617 patients from 2002 to 2014 at Mzuzu Central Hospital (MCH). No inclusion and exclusion criteria were followed. Data was analysed using excel (Microsoft office, USA) and GraphPad prism 7 software programs. Results: The most prevalent isolates were S. aureus (34.7%, n = 783), Klebsiella species (17.4%, n = 393) and Proteus species (11.4%, n = 256). Most microorganisms were isolated from adults (88.3%, n = 3889) and pus was the main source (69.3%, n = 1224). S. pneumoniae was predominantly isolated from cerebrospinal fluid (60.3%, n = 44) largely collected from children (88.2%, n = 64). Overall, most bacteria exhibited high resistance to all regularly used antimicrobials excluding ciprofloxacin. Conclusions: Our report demonstrates an increase in bacterial infection burden in sites other than blood stream and subsequent increase in prevalence of antimicrobial resistance for all major isolates. Creating an epidemiological survey unit at MCH will be essential to help inform better treatment and management options for patients with bacterial infections

Fungal ecology: principles and mechanisms of colonization and competition by saprotrophic fungi

Decomposer fungi continually deplete the organic resources they inhabit, so successful colonization of new resources is a crucial part of their ecology. Colonization success can be split into (i) the ability to arrive at, gain entry into, and establish within a resource and (ii) the ability to persist within the resource until reproduction and dissemination. Fungi vary in their life history strategies, the three main drivers of which are stress (S-selected), disturbance (ruderal, or R-selected), and incidence of competitors (C-selected); however, fungi often have combinations of characteristics from different strategies. Arrival at a new resource may occur as spores or mycelium, with successful entry and establishment (primary resource capture) within the resource largely dependent on the enzymatic ability of the fungus. The communities that develop in a newly available resource depend on environmental conditions and, in particular, the levels of abiotic stress present (e.g., high temperature, low water availability). Community change occurs when these initial colonizers are replaced by species that are either more combative (secondary resource capture) or better able to tolerate conditions within the resource, either through changing abiotic conditions or due to modification of the resource by the initial colonizers. Competition for territory may involve highly specialized species-specific interactions such as mycoparasitism or may be more general; in both cases combat involves changes in morphology, metabolism, and reactive oxygen species production, and outcomes of these interactions can be altered under different environmental conditions. In summary, community development is not a simple ordered sequence, but a complex ever-changing mosaic

Process Development for Enhanced 2,3-Butanediol Production by Paenibacillus polymyxa DSM 365

While chiral 2,3-Butanediol (2,3-BD) is currently receiving remarkable attention because of its numerous industrial applications in the synthetic rubber, bioplastics, cosmetics, and flavor industries, 2,3-BD-mediated feedback inhibition of Paenibacillus polymyxa DSM 365 limits the accumulation of higher concentrations of 2,3-BD in the bioreactor during fermentation. The Box-Behnken design, Plackett-Burman design (PBD), and response surface methodology were employed to evaluate the impacts of seven factors including tryptone, yeast extract, ammonium acetate, ammonium sulfate, glycerol concentrations, temperature, and inoculum size on 2,3-butanediol (2,3-BD) production by Paenibacillus polymyxa DSM 365. Results showed that three factors; tryptone, temperature, and inoculum size significantly influence 2,3-BD production (p < 0.05) by P. polymyxa. The optimal levels of tryptone, inoculum size, and temperature as determined by the Box-Behnken design and response surface methodology were 3.5 g/L, 9.5%, and 35 °C, respectively. The optimized process was validated in batch and fed-batch fermentations in a 5-L Bioflo 3000 Bioreactor, and 51.10 and 68.54 g/L 2,3-BD were obtained, respectively. Interestingly, the production of exopolysaccharides (EPS), an undesirable co-product, was reduced by 19% when compared to the control. These results underscore an interplay between medium components and fermentation conditions, leading to increased 2,3-BD production and decreased EPS production by P. polymyxa. Collectively, our findings demonstrate both increased 2,3-BD titer, a fundamental prerequisite to the potential commercialization of fermentative 2,3-BD production using renewable feedstocks, and reduced flux of carbons towards undesirable EPS production

The mycelial response of the white-rot fungus, Schizophyllum commune to the biocontrol agent, Trichoderma viride

In this study, agar plate interaction between Schizophyllum commune and Trichoderma viride was investigated to characterise the physiological responses occurring during interspecific mycelial combat. The metabolite profiles and morphological changes in both fungi paired on agar were studied relative to the modulation of phenoloxidase activity in S. commune. The calcium ionophore A23187 was incorporated in self-paired cultures of S. commune to explore possible involvement of calcium influx in the response of S. commune to T. viride. The levels of lipid peroxides and protein carbonyls in the confronted mycelia of S. commune were also measured. Contact with T. viride induced pigmentation and cell wall hydrolysis in S. commune with concomitant increase in phenoloxidase activity, rise in the levels of oxidative stress indicators and increased levels of phenolic compounds, antioxidant γ-amino butyric acid, and pyridoxine and osmo-protective sugar alcohols. Calcium ionophore mimicked the pigmentation in the T. viride-confronted mycelia of S. commune, implicating calcium influx in the response to T. viride. The changes in S. commune are indicative of targeted responses to osmotic and oxidative stresses and phenoloxidase-mediated detoxification of noxious compounds in the contact interface with T. viride, which may confer resistance in natural environments