Marine microbial eukaryotic diversity, with particular reference to fungi: Lessons from prokaryotes

388-398Novel molecular, analytical and culturing techniques have resulted in dramatic changes in our approaches towards marine eukaryotic diversity in recent years. This article reviews marine fungal diversity in the light of current knowledge, citing examples of how progress in understanding marine prokaryotes has often contributed to this new approach. Both ‘true fungi’ (termed mycenaean fungi in this review) and straminipilan fungi are considered. Molecular phylogenetic studies of prokaryotes has resulted in their redefinition as belonging to the Kingdoms Bacteria and Archaea. Likewise, major refinements have taken place in the phylogenetic classification of eukaryotes. In the case of fungi, it has now been realized that they are polyphyletic, belonging to the Kingdom Mycenae (Fungi), as well as the Kingdom Straminipila or Chromista. Although the total number of fungi on earth is estimated to be about 1.5 million, only a meagre number of obligate marine fungi , about 450 mycenaean and 50 straminipilan fungi have been described so far. It is likely that most of the true marine fungi have not yet been discovered. These are likely to have evolved between 1,500 million years ago (Ma) when fungi probably evolved in the sea and 900 Ma when they conquered land together with green plants. It now appears that most of the true marine fungi have not been cultured so far, similar to the ‘great plate count anomaly’ of bacteria. Thraustochytrids, which are abundant in the water column, but not easily culturable from that source is an example. Intelligent and novel culture methods might bring forth unusual and new marine fungi, as happened in the case of Pelagibacter ubique belonging to the SAR 11 group of bacteria. Molecular techniques might bring to light novel marine fungi, as is happening with bacteria. Such fungi may defy our conventional wisdom regarding these organisms in terms of morphology. Thus, several recent studies using 18S rRNA gene community profiles have discovered picoplanktonic marine fungi in the water column. Studies such as those on molecular diversity of eukaryotes in permanently anoxic habitats have also indicated that fungi may be abundant in exotic habitats and possess unusual physiology. A search for fungi in biodiversity-rich habitats, such as the coral reefs and the deep-sea, using a combination of molecular and novel culture methods is likely to reveal a fascinating diversity of marine fungi

Marine biotechnology: An approach based on components, levels and players

609-619Marine biotechnology may be viewed from the perspective of three issues, namely components, levels of research and the players or researchers. (1) The three components are organisms, applications and processes. Access to known organisms and the discovery of unique ones are basic requirements. Sustainable harvesting is the key for accessing marine invertebrates. An alternative is the development of cell culture methods and ecosystem conservation. Establishment of microbial culture collections of organisms difficult to access or cultivate, such as deep-sea and anaerobic microbes, obligate marine fungi and phytoplankton is an important facilitator. Extremophilic organisms from the deep-sea and cold environments are useful candidates for novel applications. Genomics and metagenomics are emerging as powerful tools in discovering useful genes. Application of organisms constitutes the second component of biotechnology. A search for candidate organisms for applications should be based on intelligent screening, while innovative applications of unique properties of organisms need to be established. The former is exemplified by novel drugs from coral reef invertebrates, marine polysaccharides and polyunsaturated fatty acids. Adhesive proteins of molluscs, biomimetics and nanolevel cell wall organization in diatoms are examples of intelligent applications. Process development and improvement for new and existing technologies are the final determinants of a technology. (2) The three levels are established, emerging and exploratory technologies. It is important to recognize this in order to decide who does what. (3) The key players are the academia and industries. Participation and collaboration of the two must be viewed in light of different levels of biotechnology. Improvement of established technologies belongs more to the realm of industries. Emerging technologies offer the best platform for their collaboration, while exploratory technologies are the domain of academic institutions

Morphology and physiology of the marine straminipilan fungi, the aplanochytrids isolated from the equatorial Indian Ocean

326-340While thraustochytrids, a group of unicellular marine straminipilan protists, have been found to be abundant in the water column, little is known of aplanochytrids. These constitute one of the 3 groups belonging to the Labyrinthulomycetes. Aplanochytrids were isolated from 34 out of 76 zooplankton samples from different strata in the 0–1000 m water column in the equatorial Indian Ocean. None of the samples yielded thraustochytrids in culture, suggesting that aplanochytrids might be more prevalent in the zooplankton samples of these waters than thraustochytrids. Fourteen isolates of aplanochytrids were studied with reference to their colony and cell morphological characteristics, carbon and nitrogen nutrition and the production of four degradative enzymes. All isolates produced proteases, but not lipase, amylase or chitinase. Major interesting features of several isolates included the production of motile amoebae, preference to pentoses and disaccharides and the common preference to glutamate. Cluster analysis based on all the characters showed no clear relations to morphological or physiological traits of the isolates, thus indicating the unreliability of these characters in taxonomy of aplanochytrids. All isolates corresponded to taxon Aplanochytrium yorkensis. The differences observed in these isolates correspond to variations in populations of A. yorkensis inhabiting zooplankton in the Indian Ocean and not related to different species of the genus

Simple electric powered plankton wheel for the production of aggregates in seawater on-board ship

37-41A new handy plankton wheel was devised for use on-board a ship. Its efficacy to generate aggregates was tested on land using coastal waters. The device successfully generated aggregates of sizes varying up to 11.3 mm2 within eleven days. During an on-board experiment with oceanic water within approximately the same time period, no visible aggregates were observed but the concentration of transparent exopolymeric particles (TEPs) increased from 14.4 to 547.8 mg eq Alginic Acid L-1 indicating successful production of aggregate precursors and requirement of longer incubation periods for the production of visible aggregates with oceanic waters

Thraustochytrid protists degrade hydrocarbons^{<b style=""> </b>}

139-145 Although thraustochytrid protists are known to be of widespread occurrence in the sea, their hydrocarbon-degrading abilities have never been investigated. We isolated thraustochytrids from coastal waters and sediments of Goa coast by enriching MPN isolation tubes with crude oil. Three isolates tested showed positive hydrophobicity of cell walls as judged by the Microbial Adhesion to Hydrocarbons (MATH) assay. Addition of Bombay High crude oil to nutrient broth slightly enhanced growth of the protists as compared to unenriched controls. Autoclaved crude oil added to sediments was degraded by 2 thraustochytrids to a much greater extent than non-autoclaved oil. Tarballs supported excellent growth of thraustochytrids when added to a peptone broth. Inoculation of thraustochytrids to tarball-enriched sediment resulted in a decrease of up to 71% of tarball contents after a month. Up to 30% of tarballs added to peptone broth was degraded by thraustochytrids in 7 days, as estimated by gravimetry and gas chromatography. Fractions above the retention time for 20°C aliphatics were degraded to a much greater degree than those below 20°C. Thraustochytrids appear to play a definite role in tar ball degradation in sediments. </smarttagtype

Fungi in the Marine Environment: Open Questions and Unsolved Problems.

Terrestrial fungi play critical roles in nutrient cycling and food webs and can shape macroorganism communities as parasites and mutualists. Although estimates for the number of fungal species on the planet range from 1.5 to over 5 million, likely fewer than 10% of fungi have been identified so far. To date, a relatively small percentage of described species are associated with marine environments, with ∼1,100 species retrieved exclusively from the marine environment. Nevertheless, fungi have been found in nearly every marine habitat explored, from the surface of the ocean to kilometers below ocean sediments. Fungi are hypothesized to contribute to phytoplankton population cycles and the biological carbon pump and are active in the chemistry of marine sediments. Many fungi have been identified as commensals or pathogens of marine animals (e.g., corals and sponges), plants, and algae. Despite their varied roles, remarkably little is known about the diversity of this major branch of eukaryotic life in marine ecosystems or their ecological functions. This perspective emerges from a Marine Fungi Workshop held in May 2018 at the Marine Biological Laboratory in Woods Hole, MA. We present the state of knowledge as well as the multitude of open questions regarding the diversity and function of fungi in the marine biosphere and geochemical cycles