Digestion of food depends on three main factors: (i) the ingested food and the extent to which the food is susceptible to the effects of digestive enzymes, (ii) the activity of the digestive enzymes and (iii) the length of time the food is exposed to the action of the digestive enzymes. Each of these factors is affected by a multitude of secondary factors. The present review highlights the experimental results on the secondary factor, enzymatic activity and possible contribution of the fish gut microbiota in nutrition. It has been suggested that fish gut microbiota might have positive effects to the digestive processes of fish, and these studies have isolated and identified the enzyme-producing microbiota. In addition to Bacillus genera, Enterobacteriaceae and Acinetobacter, Aeromonas, Flavobacterium, Photobacterium, Pseudomonas, Vibrio, Microbacterium, Micrococcus, Staphylococcus, unidentified anaerobes and yeast are also suggested to be possible contributors. However, in contrast to endothermic animals, it is difficult to conclude the exact contribution of the gastrointestinal microbiota because of the complexity and variable ecology of the digestive tract of different fish species, the presence of stomach and pyloric caeca and the relative intestinal length. The present review will critically evaluate the results to establish whether or not intestinal microbiota do contribute to fish nutrition.

Enzyme‐producing bacteria isolated from fish gut: a review

Diversity and ecology of psychrophilic microorganisms.

The recent availability of sequence data from many yeast species has provided important insights into our understanding of the evolutionary mechanisms in this organism and other eukaryotes. This progress is discussed here, with a focus on the evolution of diverse yeast genome architectures and the multiphyletic origins of yeast among fungi. Over the past few years, genome sequences have become available from an increasing range of yeast species, which has led to notable advances in our understanding of evolutionary mechanisms in eukaryotes. Yeasts offer us a unique opportunity to examine how molecular and reproductive mechanisms combine to affect genome architectures and drive evolutionary changes over a broad range of species. This Review summarizes recent progress in understanding the molecular mechanisms — such as gene duplication, mutation and acquisition of novel genetic material — that underlie yeast evolutionary genomics. I also discuss how results from yeasts can be extended to other eukaryotes.

Yeast evolutionary genomics

Fungi are phylogenetically and functionally diverse ubiquitous components of almost all ecosystems on Earth, including aquatic environments stretching from high montane lakes down to the deep ocean. Aquatic ecosystems, however, remain frequently overlooked as fungal habitats, although fungi potentially hold important roles for organic matter cycling and food web dynamics. Recent methodological improvements have facilitated a greater appreciation of the importance of fungi in many aquatic systems, yet a conceptual framework is still missing. In this Review, we conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring aquatic food webs. We focus on currently unexplored fungal diversity, highlighting poorly understood ecosystems, including emerging artificial aquatic habitats.

/pdf/fungi-in-aquatic-ecosystems-30synhoip6.pdf

Fungi in aquatic ecosystems

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.

/pdf/fungi-in-the-marine-environment-open-questions-and-unsolved-2coquigntf.pdf

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

Yeasts are ubiquitous in their distribution and populations mainly depend on the type and concentration of organic materials. The distribution of species, as well as their numbers and metabolic characteristics were found to be governed by existing environmental conditions. Marine yeasts were first discovered from the Atlantic Ocean and following this discovery, yeasts were isolated from different sources, viz. seawater, marine deposits, seaweeds, fish, marine mammals and sea birds. Near-shore environments are usually inhabited by tens to thousands of cells per litre of water, whereas low organic surface to deep-sea oceanic regions contain 10 or fewer cells/litre. Aerobic forms are found more in clean waters and fermentative forms in polluted waters. Yeasts are more abundant in silty muds than in sandy sediments. The isolation frequency of yeasts fell as the depth of the sampling site is increased. Major genera isolated in this study were Candida, Cryptococcus, Debaryomyces and Rhodotorula. For biomass estimation ergosterol method was used. Classification and identification of yeasts were performed using different criteria, i.e. morphology, sexual reproduction and physiological/biochemical characteristics. Fatty acid profiling or molecular sequencing of the IGS and ITS regions and 28S gene rDNA ensured accurate identification.

https://dyuthi.cusat.ac.in/xmlui/bitstream/handle/purl/2035/Marine%20yeasts-a%20rewiew.pdf;sequence=1

Marine yeasts — a review

Yeasts are ubiquitous in distribution and are found throughout the aquatic environment. Their distribution and population depends mainly on the surrounding environment. This study is about the occurrence and distribution of yeasts from the slope sediments of Arabian Sea and Bay of Bengal. Sediment samples were collected from 200, 500 and 1000 m depths along the west and east coast of Indian peninsula. Majority of sampling stations showed a clayey silt sediment texture. Organic matter was found to be comparatively higher in the Arabian Sea. Yeast population varied between stations and found to be more in Arabian Sea. Candida was the predominant genera identified from both Arabian Sea and Bay of Bengal. Diversity was maximum at 500 m in Arabian Sea and at 1000 m in Bay of Bengal. Data analysis was carried out using PRIMER 5.1 and SPSS 10.0. Correlation studies using PRIMER software showed a positive correlation between organic matter and yeast population.

https://www.imedpub.com/articles/marine-yeasts-in-the-slope-sediments-of-arabian-sea-and-bay-of-bengal.pdf

Marine yeasts in the slope sediments of Arabian sea and bay of Bengal

Marine yeasts from the slope sediments of Arabian sea and Bay of Bengal

Occurrence of black yeasts in the slope sediments of Bay of Bengal was investigated during FORV Sagar Sampada cruises 236 and 245. The black yeast population was found to be very scanty in the area and the isolates could be obtained from 200m to 1000m depth regions in the slope sediments. The isolates were identified as Hortaea werneckii by Internal Transcribed Spacer (ITS) sequencing. The biodegradation potential of these strains was found to be very high with all the strains exhibiting protease, lipase and amylase production. The optimum growth conditions were pH 8, salinity 30 ppt and temperature 30 o C. The pigment melanin, in these organisms was identified to be of dihydroxynaphthalene type by NMR. The melanin was found to exhibit inhibitory activity against different human and fish pathogens. Melanin degrading enzyme could also be extracted from these organisms.

/pdf/black-yeasts-from-the-slope-sediments-of-bay-of-bengal-3wk1r5o1y9.pdf

Black yeasts from the slope sediments of Bay of Bengal: phylogenetic and functional characterization

Marine yeasts are versatile agents of biodegradation. They act on varied substrates and helps in nutrient recycling. This study mainly focuses on the hydrolytic potential of the marine yeast isolates obtained from the slope sediments of Arabian Sea and Bay of Bengal. The optimum growth conditions like temperature, salinity and pH of the isolates were also determined. The isolates from Bay of Bengal showed more enzyme production than those of Arabian Sea. All the isolates were lipolytic. Oxidative forms were more in abundance than the fermentative forms. Black yeasts obtained from the study area, showed maximum hydrolytic potential than compared to their counter parts. Majority of the isolates preferred 30οC, pH 6 and 15 ppt salinity for maximal growth

/pdf/yeast-isolates-from-the-slope-sediments-of-arabian-sea-and-204qifaq7s.pdf

Sreedevi N. Kutty

Papers

Marine yeasts — a review

Marine yeasts in the slope sediments of Arabian sea and bay of Bengal

Marine yeasts from the slope sediments of Arabian sea and Bay of Bengal

Black yeasts from the slope sediments of Bay of Bengal: phylogenetic and functional characterization

Yeast isolates from the slope sediments of Arabian Sea and Bay of Bengal:Physiological characterization