Cryptoendolithic microorganisms from Antarctic sandstone of Linnaeus Terrace (Asgard Range): diversity, properties and interactions

Abstract

Cryptoendolithic microorganisms from stratified communities in Antarctic sandstone were studied for physiological diversity and possible interactions. Cultures of 25 bacteria, five fungi, and two green algae from one boulder grew with a wide variety of organic carbon or nitrogen sources, they exhibited varied exoenzymatic activities and were psychrophilic or psychrotrophic. Many isolates excreted vitamins into the medium and were stimulated by other vitamins. Organic acid excretion and siderophore formation were common, but antibiotic activity was rare. Plasmids were found in 24% of the bacteria, and many of these strains showed resistance to antibiotics and heavy metals. A small plasmid (2.9 kb) from strain AA-341 was electrotransferred into sensitive isolates, thereby rendering these resistant to ampicillin and Cr 3÷. Bacterial cultures in spent algal medium and coculture with algae demonstrated beneficial (rarely inhibitory) interactions. A search for free organic compounds in zones of the sandstone community revealed sugars, sugar alcohols, organic acids and amino acids -in many cases the same compounds that were excreted into the laboratory medium. Data presented here indicate low taxonomic but high physiological diversity among these heterotrophic cryptoendoliths. This physiological diversity, as well as the spatial separation in layers with distinct activities, allows coexistence within the community and contributes to the stability of this ecosystem.

Characterization of heavy metals resistant heterotrophic bacteria from soils in the Windmill Islands region, Wilkes Land, East Antarctica

“…Antibiotic resistance genes are often located on plasmids that are able to be horizontally transferred into diverse bacterial popula− tions contributing to the widespread dissemination of antibiotic resistance in the en− vironment (Davison 1999;Michaud et al 2004). Antibiotic−resistant bacteria have also detected in cold environments such as sandstones in McMurdo valley, Antarc− tica (Siebert et al 1996); the Arctic permafrost subsoil in Siberia (Mindlin et al 2008); near Palmer Station, Antarctica (Miller et al 2009); West Antarctica King George Island (Wong et al 2011); glacier environments in the Arctic, Antarctic, Central Asia, North and South America (Segawa et al 2013).…”

Antimicrobial activity and resistance to heavy metals and antibiotics of heterotrophic bacteria isolated from sediment and soil samples collected from two Antarctic islands

“…Antibiotic resistance genes are often located on plasmids that are able to transfer horizontally among diverse bacterial populations, thus contributing to the widespread dissemination of antibiotic resistance in the environment (Davison 1999;Herreros et al 2005). Antibiotic resistance has also been reported among bacteria in cold environments such as Antarctic sandstone in McMurdo Valley (Siebert et al 1996), the Arctic permafrost subsoil in Siberia (Mindlin et al 2008), Antarctic King George Island (Wong et al 2011), and seawater and penguin faecal samples collected near Palmer Station, Antarctica (Miller et al 2009). A high frequency of bacteria resistant to antibiotics can be viewed as an indicator of environmental pollution (Zhang et al 2009).…”

Genetic signatures indicate widespread antibiotic resistance and phage infection in microbial communities of the McMurdo Dry Valleys, East Antarctica

“…This is mediated by antimicrobial (antibiotic) compounds which are secreted by many phyla, and these inhibit the growth and activity of competing taxa (Hibbing et al 2010). Studies of bacteria isolated from DV soils have shown they are susceptible to antibiotics in vitro (Siebert et al 1996). However, there is no information on how widespread the ability to defend against antibiotics is among DV microorganisms.…”