The biosorption of particulates and metal ions by fungal mycelium.

Particulate adsorption by Mucor flavus and Neurospora crassa is a physical property of the cell wall, independent of both cellular metabolism and the production of extracellular polymers. Initial attractive forces responsible for particulate adsorption by N. crassa are mainly electrostatic in nature and this mechanism probably holds for M. flavus also. The outer glucan layer of the cell wall of N. crassa, although able to adsorb particulates, was not as efficient as the underlying protein layer at particle adsorption. Young, growing mycelium generally adsorbs the , -, largest amount of particles, due to the continued production of adsorption sites and the entrapment of particulates by hyphae. Factors increasing adsorption include nutrient starvation of mycelium and incubation with low concentrations of magnesium ions. Relatively high concentrations of mercury and copper ions decrease adsorption perhaps due to the precipitation and adsorption of the corresponding metal sulphides on the mycelial surface thereby effectively physically interfering with further particulate adsorption. Optimum conditions for adsorption are a temperature of 250C and a slightly acid pH value. Also, small particles are more readily adsorbed than large particles. Mucor flavus can adsorb clays and this ability may be used to treat industrial effluents which contain large amounts of clay minerals. An acid pH and a temperature of 250C are optimum conditions for clay adsorption by the fungus. Low concentrations of montmorillonite and kaolinite increase biomass production by Aspergillus niger in submerged culture, due to the inhibition of pellet formation by the fungus. The clays cause A. niger to grow in a more filamentous form and presumably would affect other fungi in a similar way. The use of clays to control fungal morphology may be important in several industrial fermentations. Low concentrations of the fungicide thiram stimulated the growth of Aspergillus niger in the presence of montmorillonite. Immobilization of fungi by magnetic means is possible due to their ability to adsorb magnetite. This method could also be used to remove fungi from fermentation media as an alternative to filtration or centrifugation. Even though older hyphae of Penicillium chrysogenum are unable to adsorb magnetite, this fungus can still be magnetically immobilized if it is grown from a spore suspension in the presence of magnetite. Either the spores or young hyphae of this fungus adsorb magnetite, producing pellets with magnetic properties. Magnetite adsorption occurs optimally at a temperature of 250C and is constant over a wide range of pH values. Waste mycelium of A. niger from the surface fermentation method of citric acid production can be magnetically removed from solution after adsorbing magnetite. Dilute solutions of sodium hydroxide and sodium bicarbonate desorbed magnetite attached to mycelial surfaces. Silver is accumulated selectively by A. niger waste mycelium produced by the surface fermentation method of citric acid production. The process is rapid, maximum uptake occurring twenty minutes after initial exposure of the mycelium to a silver solution. Silver accumulation by the mycelium is relatively insensitive to changes in pH and temperature, a slight decrease in uptake only occurring at a temperature of 800C. Dilute solutions of H2S04 and HNO3 desorb silver from the mycelial surface. However, this process is relatively inefficient and more effective desorbents need to be found to make the silver accumulation process economically viable

Soil Fungal Community Responses to the Silver Nanoparticles Contamination as Assessed by Illumina Next Generation Sequencing (NGS)

The increasing use of silver nanoparticles (AgNPs) due to its excellent antimicrobial activity in commercial products prompting concerns about their fate in the environment. The toxicity of AgNPs is mainly the result of Ag+ ions. In this study, soil was experimentally contaminated with 100 mg kg-1 of AgNO3 to investigate its effect on fungal soil community. Deoxyribonucleic acid (DNA) from the soil was extracted at the 6th, 12th, and 24th month of observation and assessed by Illumina Next Generation Sequencing (NGS). The results show that, the pollutant change fungal community in soil. After 12 months incubated the number of fungal species in the soil reduced significantly and 40% of the community was dominated by one species

Ranging behaviour and seasonal movements of Sumatran orangutans (Pongo pygmaeus abelii) in swamp forests

The ranging behaviour of Sumatran orangutans was studied in a swamp forest within the Leuser Ecosystem, Sumatra, Indonesia. The use of line transect techniques for estimating orangutan densities from nests was also examined. The densities obtained, in conjunction with raw numbers of new nests along transects were then compared with estimates of forest productivity in an attempt to identify how orangutan movements are influenced by resource availability. Using nests as an indicator of orangutan numbers produced serious underestimates of absolute densities for a variety of reasons. These were considered to stem mostly from the use of decay rates estimated from total time to nest disappearance, whilst under­detecting older nests in censuses, and from the difficulties of detecting nests on or above transects and accurately estimating distances. The number of new nests along a transect was still considered a reliable indicator of fluctuations in absolute densities. Orangutan home ranges at Suaq Balimbing were found to be distinctly larger than previously reported elsewhere. Females appear to utilise core areas of at least 500 ha, whilst also using a peripheral excursion zone so that total home ranges probably lie between 900 ha and 1500 ha. Adult male and subadult male ranges were considered to be in excess of 3000 ha and perhaps as much as 10000 ha. There was no evidence that adult females or adult males need necessarily be transient or nomadic as previously proposed. Subadult males, however, may constitute a dispersal phase. Orangutan movements were related to fruit availability, in that they will move to areas where fruit is abundant, but also into other areas when fruit is generally scarce. Thus there was evidence that orangutans shift diets during lean periods rather than travelling large distances. There was no evidence to support the occurrence of large-scale seasonal movements of orangutans. There was evidence to suggest that dominant adult males behave differently to other, non-dominant males, in that they occupy smaller ranges, probably as a result of being able to restrict access by other males to receptive females. Non-dominant adult males tended to avoid the dominant male, whereas subadult males did not. Evidence was also found to support the existence of clusters of females with similar ranges, who may be related, preferentially associate with each other, and are to some degree synchronised reproductively

THE EFFECT OF LOW LEVEL OF OZONE ON GROWTH AND DEVELOPMENT OF RHIZOPUS SP. IN VITRO

Postharvest diseases caused by microbial pathogens account for a great loss every year. Fungicides have been used for decade to control spoilage in conventional agriculture. It is generally known that long term use of chemical would harm the environment and bring resistance to organisms. Increasing public concern over the use of conventional fungicide due to health issues has prompted investigations to find alternative environmentally friendly control agent that might be used to suppress diseases development in storage.Ozone has been considered by researchers as an effective alternative to the use of traditional pesticides in food preservation because it leaves no residue on fresh produce so that safer to consumed.This work determined the effect of low level ozone exposure (180 ppb) on colony development and spores production of Rhizopus oryzae, R. stolonifer and R. microsporus var.chinensis in vitro. Two types of inocula were used, mycelial and spore, as both are responsible for spread of spoilage when stored with uncontaminated food. The tested fungi were stored in an ozone chamber at 7-8 oC for 14 days. Colony development was studied by measuring the colony diameter while spores production by time fungi was assed on the 14th day of the incubation period. Ozone exposure at 180 ppb has varied result on colony development and spore production on each species examined.Overall the work suggests that continuous low level of ozone exposure at 180 ppb for 14 days has different effect on different species depend on the ability each microorganism to counteract with ozone exposure

Differential tolerance of Trichoderma harzianum and Rhizoctonia solani towards silver nanoparticles: potential for agricultural applications?

In the previous study, we examined the effect of silver nanoparticles (AgNPs) on beneficial soil fungus including Trichoderma harzianum (T22), and pathogenic soil-borne fungus, Rhizoctonia solani (AG3-PT). The result exhibited that T. harzianum (T22) is tolerance towards AgNPs. On the other hand, the pathogenic fungi, R.solani (AG3-PT), is more sensitive to AgNPs. T. harzianum is well known as biocontrol agent to suppress R. solani. Therefore, in this study we investigated the combination of T. harzianum (T22) and AgNPs at low concentration to control two strains of R. solani (AG3-PT and AG2-1). The effect of AgNPs at two different levels (20 mg L-1 and 50 mg L-1) was examined over the growth of the two strains of R. solani and T. harzianum (T22) using dual culture technique. The results shows that this combination have a potential to reduce colony growth of R. solani (AG2-1) at higher AgNPs concentration. However, it was not the case for R. solani (AG3-PT). It can be concluded that AgNPs toxicity depend on several factors including species strain and the size of AgNPs particle

Isolation of Indigenous Hydrocarbon Transforming Bacteria from Oil Contaminated Soils in Libya: Selection for Use as Potential Inocula for Soil Bioremediation

The Libyan oil industry has left a significant legacy of contamination and methods are required to remediate oil-contaminated soils in the area. In this work hydrocarbon utilizing microorganisms were isolated and identified from contaminated soil samples obtained from an oil Refinery (Zawia, Libya). After initial screening of eleven isolates capable of growth on hexadecane, the five most promising hydrocarbon–utilizing bacteria were isolated and tested for biosurfactant production and emulsification activity. They were identified (using 16S rRNA sequence analysis) as Pseudomonas putida, Pseudomonas species, Betaproteobacterium, Actinomyces species, and Bacillus species. Among the five species tested, Pseudomonas putida showed superior performance in terms of growth on hydrocarbons (1.0×10 10 CFU (ml)), E24 emulsifying activity (86%) and ability to transform hydrocarbons in pure culture. Interestingly, gas chromatographic analysis of crude oil treated with P. putida showed a decrease in heavy hydrocarbon fractions demonstrating a clear potential for this microbe to be used as a soil inoculant in bioremediation

Apes in Space: Saving an Imperilled Orangutan Population in Sumatra

Deforestation rates in Sumatra are amongst the highest in the tropics. Lowland forests, which support the highest densities of orangutans, are particularly vulnerable to clearance and fragmentation because they are highly accessible. Consequently, many orangutans will, in the future, live in strictly or partially isolated populations. Whilst orangutans have been extensively studied in primary forests, their response to living in human-dominated landscapes remains poorly known, despite it being essential for their future management. Here, we focus on an isolated group of critically endangered Sumatran orangutans (Pongo abelii) that co-exist with farmers in a mixed agroforest system consisting of degraded natural forest, smallholder (predominantly rubber) farms and oil palm plantations. Over 24 months we conducted the first ever spatial assessment of orangutan habitat use in the human-transformed landscape of Batang Serangan, North Sumatra. From 1,204 independent crop-raiding incidents recorded, orangutans showed strong foraging preference for mixed farmland/degraded forest habitat over oil palm patches. The core home range areas of the eight adult orangutans encompassed only 14% of the available study area. Monthly home range sizes averaged 423 ha (±139, SD) for males, and 131±46 ha for females, and were positively influenced by wild and cultivated fruit presence, and by crop consumption. The average daily distance travelled was similar for both adult males (868 m±350, SD) and females (866 m±195), but increased when orangutans raided crops. These findings show that orangutans can survive, demographically, in certain types of degraded landscapes, foraging on a mixture of crops and wild fruits. However, the poor quality habitat offered to orangutans by oil palm plantations, in terms of low food availability and as a barrier to female movements, is cause for concern since this is the land use type that is most rapidly replacing the preferred forest habitat across both Sumatran and Bornean orangutan ranges

Soil contamination with silver nanoparticles reduces Bishop pine growth and ectomycorrhizal diversity on pine roots.

Soil contamination by silver nanoparticles (AgNP) is of potential environmental concern but little work has been carried out on the effect of such contamination on ectomycorrhizal fungi (EMF). EMF are essential to forest ecosystem functions as they are known to enhance growth of trees by nutrient transfer. In this study, soil was experimentally contaminated with AgNP (0, 350 and 790 mg Ag/kg) and planted with Bishop pine seedlings. The effect of AgNP was subsequently measured, assessing variation in pine growth and ectomycorrhizal diversity associated with the root system. After only 1 month, the highest AgNP level had significantly reduced the root length of pine seedlings, which in turn had a small effect on above ground plant biomass. However, after 4 months growth, both AgNP levels utilised had significantly reduced both pine root and shoot biomass. For example, even the lower levels of AgNP (350 mg Ag/kg) soil, reduced fresh root biomass by approximately 57 %. The root systems of the plants grown in AgNP-contaminated soils lacked the lateral and fine root development seen in the control plants (no AgNP). Although, only five different genera of EMF were found on roots of the control plants, only one genus Laccaria was found on roots of plants grown in soil containing 350 mg AgNP/kg. At the higher levels of AgNP contamination, no EMF were observed. Furthermore, extractable silver was found in soils containing AgNP, indicating potential dissolution of silver ions (Ag+) from the solid AgNP

Sources and contamination routes of microbial pathogens to fresh produce during field cultivation: A review

Foodborne illness resulting from the consumption of contaminated fresh produce is a common phenomenon and has severe effects on human health together with severe economic and social impacts. The implications of foodborne diseases associated with fresh produce have urged research into the numerous ways and mechanisms through which pathogens may gain access to produce, thereby compromising microbiological safety. This review provides a background on the various sources and pathways through which pathogenic bacteria contaminate fresh produce; the survival and proliferation of pathogens on fresh produce while growing and potential methods to reduce microbial contamination before harvest. Some of the established bacterial contamination sources include contaminated manure, irrigation water, soil, livestock/ wildlife, and numerous factors influence the incidence, fate, transport, survival and proliferation of pathogens in the wide variety of sources where they are found. Once pathogenic bacteria have been introduced into the growing environment, they can colonize and persist on fresh produce using a variety of mechanisms. Overall, microbiological hazards are significant; therefore, ways to reduce sources of contamination and a deeper understanding of pathogen survival and growth on fresh produce in the field are required to reduce risk to human health and the associated economic consequences

Investigation of potential reasons for bacterial survival on ‘ready-to-eat’ leafy produce during exposure to gaseous ozone

Fresh leafy produce, such as lettuce and coriander, are subject to post-harvest microbial contamination and decay. Because of increasing pesticide resistance and consumer pressures, alternative residue-free treatments, such as ozone, are being actively explored and encouraged to reduce microbial loads and curb spoilage of crops in storage/transit. However, several researchers have reported that a component of the bacterial population on leaf surfaces is resistant to ozone treatment. To investigate the potential reasons for this bacterial survival, confocal microscopy was used to visualise microbes on leaf surfaces before and after ozone treatment. Direct observation (live/dead cell staining) of cells after ozone exposure showed that some cells were still alive; this included cells in small colonies as well as individual cells. We hypothesised that cell (colony) age and prior stress (cold) contributes to, or is responsible for, the ozone resistance observed. Interestingly, cells derived from older agar-grown colonies (7–12-day-old) and cold stressed cells of a Pseudomonas sp. (isolated from coriander) showed higher ozone resistance than that of control cells (4-day-old colonies). These findings suggest that a range of factors are responsible for ozone resistance and further work to improve our understanding of the mechanisms of ozone resistance may lead to improved methods to reduce microbial spoilage of fresh produce