The Potential Role of Marine Fungi in Plastic Degradation – A Review

Plastic debris has been accumulating in the marine realm since the start of plastic mass production in the 1950s. Due to the adverse effects on ocean life, the fate of plastics in the marine environment is an increasingly important environmental issue. Microbial degradation, in addition to weathering, has been identified as a potentially relevant breakdown route for marine plastic debris. Although many studies have focused on microbial colonization and the potential role of microorganisms in breaking down marine plastic debris, little is known about fungi-plastic interactions. Marine fungi are a generally understudied group of microorganisms but the ability of terrestrial and lacustrine fungal taxa to metabolize recalcitrant compounds, pollutants, and some plastic types (e.g., lignin, solvents, pesticides, polyaromatic hydrocarbons, polyurethane, and polyethylene) indicates that marine fungi could be important degraders of complex organic matter in the marine realm, too. Indeed, recent studies demonstrated that some fungal strains from the ocean, such as Zalerion maritimum have the ability to degrade polyethylene. This mini-review summarizes the available information on plastic-fungi interactions in marine environments. We address (i) the currently known diversity of fungi colonizing marine plastic debris and provide (ii) an overview of methods applied to investigate the role of fungi in plastic degradation, highlighting their advantages and drawbacks. We also highlight (iii) the underestimated role of fungi as plastic degraders in marine habitats

MANGROVE GROWTH PROMOTION BY ENDOPHYTIC ACTINOBACTERIA AND SEAWEED EXTRACT

In this study, I aimed to determine the impact of the application of a commercial seaweed extract (SWE) bio-stimulant and endophytic actinobacterial isolates on growth performance and endogenous hormonal levels of mangroves. Therefore, I isolated endophytic plant growth promoting (PGP) actinobacteria (PGPA) from mangrove roots; and evaluated their potential as biological inoculants on mangrove seedlings under greenhouse and open-field nursery conditions. Seven salt tolerant isolates had the ability to produce different levels of in vitro plant growth regulators (PGRs) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD), and to solubilize phosphorus. Accordingly, only one isolate, Streptomyces tubercidicus UAE1 (St), was selected based on its relative superiority in displaying multiple modes of action and in successfully colonizing mangrove tissues for 15 weeks. In the greenhouse experiments, plants treated with either St or SWE significantly (P\u3c0.05) improved dry biomass by 40.2 and 55.1% in roots and 42.2 and 55.4% in shoots, respectively compared to seawater-irrigated non-treated mangrove plants (control). However, St+SWE caused a greater significant (P\u3c0.05) increase in dry weight of roots (67.6%) and shoots (65.7%) than control plants. Following the combined treatment of St+SWE, in planta PGR levels were found to be greatly enhanced over the non-treated control or treated plants grown in sediments inoculated with St or supplied with SWE only. This was evident from the significant (P\u3c0.05) increases in the photosynthetic pigments and production of PGRs, as well as the reduction in the endogenous ACC levels of plant tissues compared to those in other treatments. Tissue nutrient contents of seedlings also increased by at least two-fold in St+SWE treatment compared to control. Similar effects were observed on all growth parameters under natural open-field nursery conditions. This report is the first in the field of marine agriculture that uses SWE as a nutrient base for actinobacteria capable of producing PGRs and ACCD. By combining St with SWE, this does not only stimulate plant growth but also potentially has additive effects on mangrove ecosystem productivity in nutrient-impoverished soils in the Arabian coastal areas

Recent progress in marine mycological research in different countries, and prospects for future developments worldwide

Early research on marine fungi was mostly descriptive, with an emphasis on their diversity and taxonomy, especially of those collected at rocky shores on seaweeds and driftwood. Subsequently, further substrata (e.g. salt marsh grasses, marine animals, seagrasses, sea foam, seawater, sediment) and habitats (coral reefs, deep-sea, hydrothermal vents, mangroves, sandy beaches, salt marshes) were explored for marine fungi. In parallel, research areas have broadened from micro-morphology to ultrastructure, ecophysiology, molecular phylogenetics, biogeography, biodeterioration, biodegradation, bioprospecting, genomics, proteomics, transcriptomics and metabolomics. Although marine fungi only constitute a small fraction of the global mycota, new species of marine fungi continue to be described from new hosts/substrata of unexplored locations/habitats, and novel bioactive metabolites have been discovered in the last two decades, warranting a greater collaborative research effort. Marine fungi of Africa, the Americas and Australasia are under-explored, while marine Chytridiomycota and allied taxa, fungi associated with marine animals, the functional roles of fungi in the sea, and the impacts of climate change on marine fungi are some of the topics needing more attention. In this article, currently active marine mycologists from different countries have written on the history and current state of marine fungal research in individual countries highlighting their strength in the subject, and this represents a first step towards a collaborative inter- and transdisciplinary research strategy

Development of tailored indigenous marine consortia for the degradation of naturally weathered polyethylene films

This study investigated the potential of bacterial-mediated polyethylene (PE) degradation in a two-phase microcosm experiment. During phase I, naturally weathered PE films were incubated for 6 months with the indigenous marine community alone as well as bioaugmented with strains able to grow in minimal medium with linear low-density polyethylene (LLDPE) as the sole carbon source. At the end of phase I the developed biofilm was harvested and re-inoculated with naturally weathered PE films. Bacteria from both treatments were able to establish an active population on the PE surfaces as the biofilm community developed in a time dependent way. Moreover, a convergence in the composition of these communities was observed towards an efficient PE degrading microbial network, comprising of indigenous species. In acclimated communities, genera affiliated with synthetic (PE) and natural (cellulose) polymer degraders as well as hydrocarbon degrading bacteria were enriched. The acclimated consortia (indigenous and bioaugmented) reduced more efficiently the weight of PE films in comparison to non-acclimated bacteria. The SEM images revealed a dense and compact biofilm layer and signs of bio-erosion on the surface of the films. Rheological results suggest that the polymers after microbial treatment had wider molecular mass distribution and a marginally smaller average molar mass suggesting biodegradation as opposed to abiotic degradation. Modifications on the surface chemistry were observed throughout phase II while the FTIR profiles of microbially treated films at month 6 were similar to the profiles of virgin PE. Taking into account the results, we can suggest that the tailored indigenous marine community represents an efficient consortium for degrading weathered PE plastics

Phylogenetic Diversity of Cyanobacteria from Qatar Coastal Waters

Cyanobacteria represent the major microorganism phyla, being diverse and widespread group inhabiting most of the earth's environments. The recent increase of occurrence of toxic cyanobacterial strains in the marine environment attracts attention of the scientific community and environmental managers. The deterministic factors leading to such events are under scrutiny and are closely linked to our understanding of the diversity and environmental response of these strains to environmental conditions. The extreme environment witnessed in the Arabian Gulf is likely to nurture the occurence of such harmful events. In recent times advanced molecular methodologies for the detection and genetic characterization of cyanobacteria were developed based on DNA amplification techniques. We aim in this work to better understand the diversity of the cyanobacterial natural communities found in Qatar marine environment through a genotypic characterization (phylogenetic analysis) with the objective to i. assess the local diversity, and ii. provide consistent reference for future comparative analysis, biotechnological applications and monitoring. In this study, QUCCCM strains from Qatar coastal were used to amplify fragments of the 16S rRNA gene followed by phylogenetic analysis. This methodology showed to produce accurate identification of the considered strains and analyze their evolutionary relationship. 28 taxa were identified among them 21.4% belong to the genus Geitlerinem, 25% Chroococcidiopsis, 10.7% Synechococcus, 10.7% Stanieria, 7.1% Euhalothece, 7.1% Geminocystis, 3.6% Leptolyngbya, 3.6% Oscillatoria, and 3.6% Dermocarpella. The biogeographic distribution of the strains and their potential toxicity is discussed

Impacts and effects of ocean warming on intertidal rocky habitats.

• Intertidal rocky habitats comprise over 50% of the shorelines of the world, supporting a diversity of marine life and providing extensive ecosystem services worth in the region of US$ 5-10 trillion per year. • They are valuable indicators of the impacts of climate change on the wider marine environment and ecosystems. • Changes in species distributions, abundance and phenology have already been observed around the world in response to recent rapid climate change. • Species-level responses will have considerable ramifications for the structure of communities and trophic interactions, leading to eventual changes in ecosystem functioning (e.g. less primary producing canopy-forming algae in the North-east Atlantic). • Whilst progress is made on the mitigation1 required to achieve goals of a lower-carbon world, much can be done to enhance resilience to climate change. Managing the multitude of other interactive impacts on the marine environment, over which society has greater potential control (e.g. overfishing, invasive non-native species, coastal development, and pollution), will enable adaptation1 in the short and medium term of the next 5-50 years

Scientific Information on Gulf of Mannar - A Bibliography

Gulf of Mannar in the southeast coast of India extends from Rameswaram Island in the north to Kanyakumari in the south. It has a chain of 21 islands stretching from Mandapam to Tuticorin to a distance of 140 km along the coast. Each one of the islands is located anywhere between 2 and 10 km from the mainland. The Gulf of Mannar Biosphere Reserve was set up on 18th February 1989 jointly by the Government of India and the state of Tamilnadu. The government of Tamilnadu in G.O. M.S. No 962 dated 10th September 1986 notified under section 35(1) of the Wildlife (Protection) Act 1972 the intention to declare the 21 islands as Marine National Park for the purpose of protecting marine wildlife and its environment including depths of 3.5 fathoms on the bay side to 5 fathoms on the seaward side. The compilation of all available scientific literature in the form of an annotated bibliography of the Gulf of Mannar biosphere reserve has brought to light the existence of nearly 3,000 publications up to date. This covers the literature published from as early as 1864 to the current year. A large number of publications in the first half of the 20th century have brought out information on the variety of fauna and flora found in the Gulf of Mannar, their biology and ecology. A lot of emphasis on the fish and fisheries research has been given only in the second half of the 20th century. Emphasis is being given on biochemical aspects of flora and fauna in the later part of the 20th century and at present

Microbial Colonisation and Degradation of Plastic Pollution in the Marine Environment

Plastic pollution is ubiquitous in the world’s oceans and is predicted to increase by an order of magnitude by 2025. The environmental impacts of plastic pollution are well documented in terms of its effects on marine animals however, the impact plastic has on the natural physicochemical characteristics of seawater and the microbial composition of the world’s oceans remains largely unknown. In particular, the role that microbial communities play in the early stages of colonisation and decomposition requires more attention. In response to this knowledge gap, both laboratory-based and field work experiments were undertaken in order to gain further insights. A microcosm experiment using natural seawater amended with range of plastics, both synthetic and biodegradable, was carried out to evaluate the impact of these plastics on the marine microbial communities. To complement this, a one-year field exposure trial was undertaken to measure biofilm formation and growth, as well as changes in polymer characteristics resulting from degradation. Finally, a biodegradation study was undertaken to identify bacteria within seawater that may degrade plastic. The characterisation of marine bacterial communities revealed major shifts in composition when plastics were introduced into seawater. These microbiological shifts were due to changes in the concentration of dissolved organic carbon, pH and total nitrogen due to the degradation of plastic materials. Furthermore, the long-term field work exposure experiment showed that different plastic substrates selected for distinct colonising communities on their surfaces. The analysis of the biofilm communities revealed the presence of bacteria that could possibly be involved in the degradation of plastics. However, no significant degradation was measured for the in situ tested plastics, suggesting that biofilm formation may have limited degradation. An exploration of plastic degradation using distinct bacterial consortia isolated from seawater resulted in biodegradation (mineralisation) figures of 16, 9 and 7 % for polyvinyl chloride, high-density polyethylene and polyethylene terephthalate respectively. In summary, results from this thesis suggest that the presence of plastic in seawater affects the microbial community by changing the inherent chemical and biological properties of the water. In addition, plastics were shown to select for distinct colonising communities, which did not contribute to the plastic degradation. However, enriched marine bacterial communities demonstrated biodegradation ability that could be explored further in the future to gain additional insights into underlying biodegradation mechanisms