Distribution, characterization, and nutrition of marine microorganisms from the algae Polysiphonia lanosa and Ascophyllum nodosum

Abstract

Quantitative studies were carried out on the bacterial populations of two associated littoral marine algae, Polysiphonia lanosa and Ascophyllum nodosum, and of the environmental seawater. Samplings conducted twice monthly from May to September, 1964, showed that numbers of bacteria on P. lanosa and in the seawater remained relatively constant while those on A. nodosum decreased in mid-summer, after an apparent spring maximum, and then gradually increased.Pure cultures of 25 isolates of frequent occurrence were studied and identified to the genus level. There was a preponderance of members of the genera Vibrio and Flavobacter (eight of each genus). Three members of the Escherichia group, two of Pseudomonas, and one belonging to each of the genera Sarcina, Staphylococcus, and Achromobacter (or Alkaligenes), as well as a pink yeast (Rhodotorula), made up the rest of the isolates.The optimum temperature for growth of most of the isolates was around 21 °C. Five of the isolates failed to grow at 30 °C. Twenty did not grow at 37 °C; of the five organisms which grew at 37 °C, growth was feeble in every case but one.Studies on the gross nutritional requirements of the marine organisms showed that 22 of the 25 isolates required a supplement of amino acids in the growth medium. Two were able to grow on basal medium; one isolate grew only in a medium supplemented with growth factors in addition to amino acids.The above findings are briefly discussed with special reference to the association between the two algae.