Fungal communities of young and mature hypersaline microbial mats

Abstract

Microbial mats are a laminated organic-sedimentary ecosystem, found in a wide range of habitats. Fluctuating diel and seasonal physicochemical gradients characterize these ecosystems, resulting in both strata and microenvironments that harbor specific microbial communities. This study was undertaken to compare two types of microbial mats across seasons to further understand the structure of fungal communities in hypersaline microbial mats and their seasonal dynamics. The structure and diversity of fungal communities was documented in young transient and mature hypersaline microbial mats from a tropical region (Puerto Rico) using one culture-dependent and three culture-independent molecular techniques based on the internal transcribed spacer (ITS) region of ribosomal DNA: terminal restriction fragment length polymorphism (TRFLP), denaturing gradient gel electrophoresis (DGGE) and clone libraries. Two microbial mats (one young and transient, one mature) were sampled in Nov 2007 (wet season), Jan 2008 (intermediate season) and Mar 2008 (dry season) in the Cabo Rojo Solar Salterns on the southwestern coast of Puerto Rico. Traditional and molecular techniques revealed strong spatial and temporal heterogeneities in both microbial mats. Higher abundance of isolates and phylotypes were observed during the wet season, and diversity decreased from the top (oxic) to the bottom (anoxic) layers in both seasons. Some of the species isolated belong to the genera Aspergillus, Cladosporium, Hortaea, Pichia and Wallemia, which often are isolated from hypersaline environments. The most abundant clones belong to Acremonium strictum and Cladosporium halotolerans, which were not isolated in pure culture. The differences observed using culture-based and molecular techniques demonstrates the need of combining methods to study the diversity of fungi in a given substrate.

Fungal evolution: major ecological adaptations and evolutionary transitions

“…Hence, it is conceivable that amoebophagous Zoopagomycota were already parasites of such amoebae, although it is very unlikely that we will find compelling fossil evidence to confirm this. Ediacaran circular fossils have been proposed to represent microbial mats (Grazhdankin & Gerdes, ; LaFlamme et al, ), and are similar to certain contemporary communities known to harbour fungi (Cantrell & Duval‐Pérez, ; Cantrell et al, ). Other authors claim these fossils are from lichens and slime moulds (Retallack, ), suggesting an already well‐developed terrestrial microbial ecosystem.…”

Microbial mats: an ecological niche for fungi

“…Cantrell and Báez-Félix (2010) using TRFLP profiles and clone libraries of the ITS region found that the community of fungi of a mature microbial mat differs between seasons, being more diverse during the rainy season when salinity decreases and oxygen concentrations increase, and that fungal diversity decreases from top (oxic) to the bottom (anoxic) layers of the mats. A recent study using the same combination of methods shows that fungal communities differ between young and transient mats that form only during the rainy season versus mature and well-developed mats that are continuously inundated (Cantrell et al, 2013). Young and transient mats have greater diversity than mature and well-developed mats.…”

Swim bladder mycosis in pretty tetra (Hemigrammus pulcher) caused by Exophiala pisciphila and Phaeophleospora hymenocallidicola, and experimental verification of pathogenicity

“…It is evident from the ITS rDNA sequences with 99–100% similarity deposited in the GenBank database that P. hymenocallidicola is predominantly an endophytic fungus with a broad spectrum of host plants, including Ardisia (Higginbotham et al., ), Eucalyptus (Crous et al., ; Marsberg, Slippers, Wingfield, & Gryzenhout, ), Ficus (Solis, Cruz, Schnittler, & Unterseher, ), Heterosmilax (Gao et al., ), Livistona (Guo, Hyde, & Liew, ), Minosops (Sopalun, ), Phryganocydia (Higginbotham et al., ) and Psychotria (Higginbotham et al., ). Phaeophleospora hymenocallidicola has also been isolated from mangrove soil (Xu, Yu, Liu, Li, & Wang, ), coral mucus (Barathikannan, Ramasamy, Manohar, & Meena, ), deep‐sea sediment (Zhang et al., ) and hypersaline microbial mats (Cantrell et al., ). We assume that the plants or wooden decorations inside the aquarium on which the fungus could grow were probably the source of infection for the fish.…”