Apparent Indispensability of Bacteria in Foraminiferan Nutrition

Abstract

SYNOPSIS. Bacteria were required for the sustained reproduction of 4 species of foraminifera in gnotobiotic culture. None of the species of algae tested, singly or in combination, supported continuous reproduction of the foraminifera in bacteria‐free gnotobiotic culture. It is inferred that bacteria have some nutritional factor required by the foraminifera that is either unavailable or unavailable in sufficient quantity in an exclusively algal diet. Gnotobiotic clones of Quinqueloculina lata, Spiroloculina hyalina, Rosalina leei , and Allogromia laticollaris were established on bacteria + algae (usually 1 or 2 species). In balanced gnotobiotic cultures neither light nor foraminiferan density (organisms/ml) were limiting. As cultures aged, pH shifted and limited growth. When waste products were removed by washing, reproductive rates were higher.