Impact of Anthropogenic Activities on Genetic Variability of Yeasts inhabiting Mangrove sediments of Dar es Salaam, Tanzania

Mangroves are coastal wetland forests established at intertidal zones of estuaries, deltas, creeks, lagoons, marshes and mudflats of tropical and subtropical latitudes (Ananda & Sridhar, 2004). Approximately one fourth of the world’s coastline is dominated by mangroves that are distributed in 112 countries and cover about 180,000 km2 of the globe’s surface in subtropical and tropical regions (Latha & Mitra, 1998). Among marine ecosystems, mangroves constitute the second most important ecosystem in productivity. Mangrove forests are believed to be an important sink of suspended sediments (Kathiresan & Bingham, 2001). In these forests, mangrove trees catch sediment by their complex aerial root structure, thus functioning as land builder (Holguin et al., 2001). They also generate considerable amount of detritus such as leaf litter and woody debris hence constitute an ideal environment that support or harbor diverse groups of marine animals, plants and microorganisms that are widely acknowledged to be important elements in coastal ecosystems in the tropics (Holguin et al., 2001). Mangroves preserve water quality and reduce pollution by filtering suspended materials and by assimilating dissolved nutrients, stabilize sediments and protect the shoreline from erosion.

In mangrove sediment communities, substantial fungal populations exist as part of the vast microbial diversity involved in detritus processing (Abdel-Wahab, 2005). Marine fungi (which are those that grow and sporulate exclusively in a marine or estuarine habitat) are major decomposers of woody and herbaceous substrata in marine ecosystems, where they also degrade dead animals (Kohlmeyer et al., 1996a). Marine fungi are the primary degraders of lignin, cellulose and other plant components in mangroves as they can synthesize all the necessary enzymes (Singh & Steinke, 1992; Bremer, 1995). Marine fungi play an important role in the complex microbial mediated nutrient cycling processes and biodegradation of xenobiotics such as petroleum and its derivatives (De Araujo et al., 1995).

Yeasts are fungi that predominantly exist as unicellular organisms and at present there are about 1500 recognized yeast species which are distributed between the ascomycetes and the basidiomycetes (Kurtzman & Fell, 2005; Botha, 2011).Yeasts play a role in maintenance of soil and sediment structure and aggregate formation. Also, Yeasts participate in soil nutrient cycles and mineralization processes. On the other hand, Yeasts serve as a nutrient source for a diversity of soil predators and they have potential as plant growth promoters and soil conditioners (Yurkov et al., 2012). However, among the marine microbiota in East Africa, it is only bacteria that have been investigated and reported (Lyimo, 1999; Machiwa, 1999; Marshal, 1994 & Mgaya et al., 2004), leaving the potential of East African fungal diversity unfamiliar.

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(Author: Eva M. Sosovele, Ken M. Hosea

 Published by Macrothink Institute)