Fungi possess the biochemical and ecological capacity to degrade environmental organic chemicals and to decrease the risk associated with metals, metalloids and radionuclides, either by chemical modification or by influencing chemical bioavailability. Furthermore, the ability of these fungi to form extended mycelial networks, the low specificity of their catabolic enzymes and their independence from using pollutants as a growth substrate make these fungi well suited for bioremediation processes. However, despite dominating the living biomass in soil and being abundant in aqueous systems, fungi have not been exploited for the bioremediation of such environments. In this Review, we describe the metabolic and ecological features that make fungi suited for use in bioremediation and waste treatment processes, and discuss their potential for applications on the basis of these strengths.

Untapped potential: exploiting fungi in bioremediation of hazardous chemicals

Bacteria and fungi can form a range of physical associations that depend on various modes of molecular communication for their development and functioning. These bacterial-fungal interactions often result in changes to the pathogenicity or the nutritional influence of one or both partners toward plants or animals (including humans). They can also result in unique contributions to biogeochemical cycles and biotechnological processes. Thus, the interactions between bacteria and fungi are of central importance to numerous biological questions in agriculture, forestry, environmental science, food production, and medicine. Here we present a structured review of bacterial-fungal interactions, illustrated by examples sourced from many diverse scientific fields. We consider the general and specific properties of these interactions, providing a global perspective across this emerging multidisciplinary research area. We show that in many cases, parallels can be drawn between different scenarios in which bacterial-fungal interactions are important. Finally, we discuss how new avenues of investigation may enhance our ability to combat, manipulate, or exploit bacterial-fungal complexes for the economic and practical benefit of humanity as well as reshape our current understanding of bacterial and fungal ecology.

Bacterial-Fungal Interactions: Hyphens between Agricultural, Clinical, Environmental, and Food Microbiologists

Sorption, transport and biodegradation - An insight into bioavailability of persistent organic pollutants in soil.

Fungi and bacteria are found living together in a wide variety of environments. Their interactions are significant drivers of many ecosystem functions and are important for the health of plants and animals. A large number of fungal and bacterial families engage in complex interactions that lead to critical behavioural shifts of the microorganisms ranging from mutualism to antagonism. The importance of bacterial-fungal interactions (BFI) in environmental science, medicine and biotechnology has led to the emergence of a dynamic and multidisciplinary research field that combines highly diverse approaches including molecular biology, genomics, geochemistry, chemical and microbial ecology, biophysics and ecological modelling. In this review, we discuss recent advances that underscore the roles of BFI across relevant habitats and ecosystems. A particular focus is placed on the understanding of BFI within complex microbial communities and in regard of the metaorganism concept. We also discuss recent discoveries that clarify the (molecular) mechanisms involved in bacterial-fungal relationships, and the contribution of new technologies to decipher generic principles of BFI in terms of physical associations and molecular dialogues. Finally, we discuss future directions for research in order to stimulate synergy within the BFI research area and to resolve outstanding questions.

Bacterial-fungal interactions: ecology, mechanisms and challenges.

The marine environment is highly susceptible to pollution by petroleum, and so it is important to understand how microorganisms degrade hydrocarbons, and thereby mitigate ecosystem damage. Our understanding about the ecology, physiology, biochemistry and genetics of oil-degrading bacteria and fungi has increased greatly in recent decades; however, individual populations of microbes do not function alone in nature. The diverse array of hydrocarbons present in crude oil requires resource partitioning by microbial populations, and microbial modification of oil components and the surrounding environment will lead to temporal succession. But even when just one type of hydrocarbon is present, a network of direct and indirect interactions within and between species is observed. In this review we consider competition for resources, but focus on some of the key cooperative interactions: consumption of metabolites, biosurfactant production, provision of oxygen and fixed nitrogen. The emphasis is largely on aerobic processes, and especially interactions between bacteria, fungi and microalgae. The self-construction of a functioning community is central to microbial success, and learning how such “microbial modules” interact will be pivotal to enhancing biotechnological processes, including the bioremediation of hydrocarbons.

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Marine crude-oil biodegradation: a central role for interspecies interactions

Contaminant biodegradation in soil is frequently limited by hindered physical access of bacteria to the contaminants. In the frame of the development of novel bioremediation approaches based on ecological principles, we tested the hypothesis that fungal networks facilitate the movement of bacteria by providing continuous liquid films in which gradients of chemoattractants can form and chemotactic swimming can take place. Unlike bacteria, filamentous fungi spread with ease in water-unsaturated soil. In a simple laboratory model of a water-unsaturated environment, we studied the movement of polycyclic aromatic hydrocarbon-degrading Pseudomonas putida PpG7 (NAH7) along a mycelium of Pythium ultimum. Some undirected dispersal was observed in the absence of a chemoattractant or when the non-chemotactic derivative strain P. putida G7.C1 (pHG100) was used. The bacterial movement became fourfold more effective and clearly directed when the chemotactic wild type was used and salicylate was present as a chemoattractant. No dispersal of bacteria was found in the absence of the fungus. These findings point at a role of mycelia for the translocation of chemicals and microorganisms. The results suggest that fungi improve the accessibility of contaminants in water-unsaturated environments.

Fungal mycelia allow chemotactic dispersal of polycyclic aromatic hydrocarbon‐degrading bacteria in water‐unsaturated systems

To cope with heterogeneous subsurface environments mycelial microorganisms have developed a unique ramified growth form. By extending hyphae, they can obtain nutrients from remote places and transport them even through air gaps and in small pore spaces, repectively. To date, studies have been focusing on the role that networks play in the distribution of nutrients. Here, we investigated the role of mycelia for the translocation of nonessential substances, using polycyclic aromatic hydrocarbons (PAHs) as model compounds. We show that the hyphae of the mycelial soil oomycete Pythium ultimum function as active translocation vectors for a wide range of PAHs. Visualization by two-photon excitation microscopy (TPEM) demonstrated the uptake and accumulation of phenanthrene (PHE) in lipid vesicles and its active transport by cytoplasmic streaming of the hyphae (‘hyphal pipelines’). In mycelial networks, contaminants were translocated over larger distances than by diffusion. Given their transport capacity and ubiq...

Mycelia promote active transport and spatial dispersion of polycyclic aromatic hydrocarbons.

Summary


Mycelia of fungi and soil oomycetes have recently been found to act as effective paths boosting bacterial mobility and bioaccessibility of contaminants in vadose environments. In this study, we demonstrate that mycelia can be used for targeted separation and isolation of contaminant-degrading bacteria from soil. In a ‘proof of concept’ study we developed a novel approach to isolate bacteria from contaminated soil using mycelia of the soil oomycete Pythium ultimum as translocation networks for bacteria and the polycyclic aromatic hydrocarbon naphthalene (NAPH) as selective carbon source. NAPH-degrading bacterial isolates were affiliated with the genera Xanthomonas, Rhodococcus and Pseudomonas. Except for Rhodococcus the NAPH-degrading isolates exhibited significant motility as observed in standard swarming and swimming motility assays. All steps of the isolation procedures were followed by cultivation-independent terminal 16S rRNA gene terminal fragment length polymorphism (T-RFLP) analysis. Interestingly, a high similarity (63%) between both the cultivable NAPH-degrading migrant and the cultivable parent soil bacterial community profiles was observed. This suggests that mycelial networks generally confer mobility to native, contaminant-degrading soil bacteria. Targeted, mycelia-based dispersal hence may have high potential for the isolation of bacteria with biotechnologically useful properties.

/pdf/use-of-mycelia-as-paths-for-the-isolation-of-contaminant-4av2pfhblu.pdf

Use of mycelia as paths for the isolation of contaminant-degrading bacteria from soil.

https://link-springer-com-443.webvpn.jmu.edu.cn/content/pdf/10.1007%2F978-3-540-77587-4_107.pdf

Shoko Furuno

Papers

Fungal mycelia allow chemotactic dispersal of polycyclic aromatic hydrocarbon‐degrading bacteria in water‐unsaturated systems

Mycelia promote active transport and spatial dispersion of polycyclic aromatic hydrocarbons.

Use of mycelia as paths for the isolation of contaminant-degrading bacteria from soil.

Fungi as Transport Vectors for Contaminants and Contaminant-Degrading Bacteria