CRYPTOENDOLITHIC MICROORGANISMS FROM ANTARCTIC SANDSTONE OF LINNAEUS TERRACE (ASGARD RANGE) - DIVERSITY, PROPERTIES AND INTERACTIONS

Cryptoendolithic microorganisms from stratified communities in Antarct ic sandstone were studied for physiological diversity and possible int eractions. Cultures of 25 bacteria, five fungi, and two green algae fr om one boulder grew with a wide variety of organic carbon or nitrogen sources, they exhibited varied exoenzymatic activities and were psychr ophilic or psychrotrophic. Many isolates excreted vitamins into the me dium 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 isolate s, thereby rendering these resistant to ampicillin and Cr3+. Bacterial cultures in spent algal medium and co-culture with algae demonstrated beneficial (rarely inhibitory) interactions. A search for free organi c compounds in zones of the sandstone community revealed sugars, sugar alcohols, organic acids and amino acids - in many cases the same comp ounds that were excreted into the laboratory medium. Data presented he re 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 c oexistence within the community and contributes to the stability of th is ecosystem.