Microstructural Characterization of Cyanobacterial Mats from the McMurdo Ice Shelf, Antarctica

Abstract

The three-dimensional structures of two types of cyanobacterium-dominated microbial mats from meltwater ponds on the McMurdo Ice Shelf were as determined by using a broad suite of complementary techniques, including optical and fluorescence microscopy, confocal scanning laser microscopy, scanning electron microscopy with back-scattered electron-imaging mode, low-temperature scanning electron microscopy, and microanalyitical X-ray energy dispersive spectroscopy. By using a combination of the different in situ microscopic techniques, the Antarctic microbial mats were found to be structures with vertical stratification of groups of cyanobacteria and mineral sediments, high contents of extracellular polymeric substances, and large void spaces occupied by water. In cyanobacterium-rich layers, heterocystous nostocalean and nonheterocystous oscillatorialean taxa were the most abundant taxa and appeared to be intermixed with fine-size deposits of epicellular silica and calcium carbonate. Most of the cyanobacterial filaments had similar orientations in zones without sediment particles, but thin filaments were tangled among thicker filaments. The combination of the microscopic techniques used showed the relative positions of biological and mineral entities within the microbial mats and enabled some speculation about their interactions.

Sources of edaphic cyanobacterial diversity in the Dry Valleys of Eastern Antarctica

“…Their dominance, particularly in lakes, ponds and on moist soils, has resulted in research on numerous aspects of their taxonomy, physiology and ecology (Vincent et al, 1993;Taton et al, 2003;de los Ríos et al, 2004). However, reports on cyanobacteria in Antarctic mineral soils are scarce and variable.…”

“…However, it is their presence in Antarctic lakes and ponds that have attracted the most interest and led to detailed research into their taxonomy (morphological and molecular), community structure, biogeographical distribution and physiology (for example, Vincent et al, 1993;Taton et al, 2003Taton et al, , 2006ade los Ríos et al, 2004;Jungblut et al, 2005;Novis and Smissen, 2006). Recent molecular-based studies on these systems have revealed a higher diversity than that documented by morphological methods and identified potentially endemic Antarctic species (Taton et al, 2003(Taton et al, , 2006a.…”

Isolation, characterization and localization of extracellular polymeric substances from the cyanobacteriumArthrospira platensisstrain MMG-9

“…EPS that surround microbes are involved in the attachment of cells to a substrate and also in the formation of a matrix in which microbes are embedded (de los Rios et al, 2004). In terrestrial cyanobacteria, a thick EPS envelope also serves as a reservoir to hold water in order to avoid desiccation (Yoshimura et al, 2012).…”

Hidden levels of phylodiversity in Antarctic green algae: further evidence for the existence of glacial refugia

“…Pyramimonas australis: Moro et al 2002;Scenedesmus sp. : Lesser et al 2002;Pocock et al 2004;lichen symbionts: Romeike et al 2002;eukaryotic clone libraries: Christner et al 2003;de la Torre et al 2003;Fell et al 2006).…”

“…coastal low-latitude regions) is, however, still elusive (Hodgson et al 2001(Hodgson et al , 2005Gibson & Bayly 2007). Life in Antarctic aquatic ecosystems is largely microbial and confined to benthic mats consisting of cyanobacteria, and to a lesser extent diatoms and green algae (Sabbe et al 2004;de los Rios et al 2004). Micro-organisms form an interesting test case in the light of the refugium hypothesis in that they are expected, within the limits of their environmental tolerance, to show ubiquitous distribution patterns as a result of their virtually unlimited dispersal capacity (but see ongoing discussion on microbial biogeography in, for example, Martiny et al 2006).…”