A NEW STRAIN OF PARATETRAMITUS JUGOSUS FROM LAGUNA FIGUEROA, BAJA CALIFORNIA, MEXICO

¹ Department of Biology, Boston University, Boston, MA 02215
² Department of Chemistry, Boston University, Boston, MA 02215
³ National Marine Fisheries Service, U. S. Department of Commerce, Oxford, MD 21654

A euryhalic, moderately temperature tolerant, fast growing strain of the amoebomastigote Paratetramitus jugosus was isolated from the North Pond flat laminated microbial mat at Laguna Figueroa, Baja California del Norte, Mexico. The morphology was studied with phase contrast, differential interference contrast, scanning, and transmission electron microscopy. On the basis of its life cycle characteristics, growth rate, salt and heat tolerance, fluorescence excitation and emission spectra, and isozymes, the organism was determined to be a new strain, P. jugosus baja californiensis. This new strain, unlike the type specimen (ATCC 30703), grows vigorously on half strength sea water and slowly at 0.51 M (nearly 3 per cent) sodium chloride. It tolerates the hypersaline conditions of the evaporite flat that prevail when the North Pond mats are dominated by Microcoleus and other bacteria, growing well during periods of influx of fresh water. Its cysts survive complete dryness of the sediment for at least three years.

The microbial mats in which this Paratetramitus jugosus has been found are thought to have Archean analogues over 3 billion years old. The discovery of resistant abundant small eukaryotes within a setting dominated by bacteria may be important for the interpretation of the Proterozoic microbial fossil record.