Strong and widespread cycloheximide resistance in Stichococcus-like eukaryotic algal taxa

This study was initiated following the serendipitous discovery of a unialgal culture of a Stichococcus-like green alga (Chlorophyta) newly isolated from soil collected on Signy Island (maritime Antarctica) in growth medium supplemented with 100 µg/mL cycloheximide (CHX, a widely used antibiotic active against most eukaryotes). In order to test the generality of CHX resistance in taxa originally identified as members of Stichococcus (the detailed taxonomic relationships within this group of algae have been updated since our study took place), six strains were studied: two strains isolated from recent substrate collections from Signy Island (maritime Antarctica) (“Antarctica” 1 and “Antarctica” 2), one isolated from this island about 50 years ago (“Antarctica” 3) and single Arctic (“Arctic”), temperate (“Temperate”) and tropical (“Tropical”) strains. The sensitivity of each strain towards CHX was compared by determining the minimum inhibitory concentration (MIC), and growth rate and lag time when exposed to different CHX concentrations. All strains except “Temperate” were highly resistant to CHX (MIC > 1000 µg/mL), while “Temperate” was resistant to 62.5 µg/mL (a concentration still considerably greater than any previously reported for algae). All highly resistant strains showed no significant differences in growth rate between control and treatment (1000 µg/mL CHX) conditions. Morphological examination suggested that four strains were consistent with the description of the species Stichococcus bacillaris while the remaining two conformed to S. mirabilis. However, based on sequence analyses and the recently available phylogeny, only one strain, “Temperate”, was confirmed to be S. bacillaris, while “Tropical” represents the newly erected genus Tetratostichococcus, “Antarctica 1” Tritostichococcus, and “Antarctica 2”, “Antarctica 3” and “Arctic” Deuterostichococcus. Both phylogenetic and CHX sensitivity analyses suggest that CHX resistance is potentially widespread within this group of algae

A PRELIMINARY INVESTIGATION OF THE DIVERSITY, SURVIVABILITY AND DISPERSAL OF ALGAE INTRODUCED INTO ANTARCTICA BY HUMAN ACTIVITY (15th Symposium on Polar Biology)

Human activity was found to be an effective vector for the dispersal of microalgae to the Ross Sea regions of Antarctica. A total of 50 taxa, mostly typical soil algae, were identified as potential colonizers. Sample material included dust on equipment and boots of expeditioners taken prior to boarding aircraft bound for Antarctica, and soil adherrent to fresh vegetables imported into Scott Base, Ross Island. 10 taxa were from genera unrecorded in the Ross Sea regions. Cylindrospermum (Cyanophyta) and Eustigmatos (Eustigmatophyta) are relatively easily recognised and their spread could be monitored if they became established in Antarctic habitats. However, there was no evidence of the establishment of any exogenous algae even in highly perturbed habitats close to Scott Base. Airborne dispersal within Antarctica was found to disperse algal propagules in the vicinity of Scott Base, although numbers were very low, being two orders of magnitude lower than those found in New Zealand. The ability of indigenous Antarctic algae and exogenous potential colonizers to survive freeze-thaw cycles, high salinity and desiccation was investigated in laboratory experiments. In general, strains isolated from dust on boots and equipment and from New Zealand air showed high survivability, as did the indigenous Antarctic strains. In contrast, strains isolated from soil on fresh vegetables imported into Antarctica had low survival similar to those isolated from a typical moist New Zealand garden soil. Suggestions are provided on how these preliminary investigations can be extended and improved

Six new species of terrestrial algae from Signy Island, South Orkney Islands, Antarctica

Six species are described and compared with related algae. All were isolated in culture from terrestrial habitats on Signy Island, South Orkney Islands, Antarctica. They are: Botrydiopsis constricta sp. nov. (Mischococcales, Xanthophyceae), Heterothrix antarctica sp. nov. (Tribonematales, Xanthophyceae), Sphaerocystis oleifera sp. nov. (Chlorococcales, Chlorophyceae), Sphaerocystis signiensis sp. nov., Sphaerocystis bilobata sp. nov. and Fottea pyrenoidosa sp. nov. (Ulothricales, Chlorophyceae)