Nutrition of Some Phagotrophic Fresh‐water Chrysomonads

Abstract

The chrysomonads are a vast array of brown-pigmented fresh-water, soil, and marine flagellates. Colorless phagotrophic counterparts of several of the pigmented species are common in nature, e.g., Molzus and Oikomonus. The minimal nutritional requirements of 4 fresh-water strains belonging to 2 species are described here. No chrysomonad previously has been grown in chemically defined media. These strains ingest particulate food and are therefore animals (protozoa) and, being to some extent phototrophic, they are plants (algae) as well. They can live indefinitely in darkness or in light on high-molecular dissolved food, as well as in low-molecular chemically defined media. This extraordinary versatility, first thoroughly documented in the pioneering pure culture study of Pring~heirn,~ is accompanied by a remarkable tolerance of variations in media and exceedingly dense growth in appropriate media, including certain simple "synthetic" media [one cannot unambiguously call "synthetic" a medium containing cobalamin (vitamin Biz), whose complete structure is still to be ascertained]. This ease of cultivation-in which respect these chrysomonads contrast sharply with some of the planktonic chrysomonadslO-suggests that the biochemical basis of an intermeshed phagotrophy and phototrophy can profitably be investigated in them.PringsheimQ reviewed the scanty previous work. He demonstrated an active phagotrophy in the same strains on which the present paper is based: They ingested starch grains, oil droplets, casein particles, bacteria, and small algae -including each other. Glucose was utilized in the presence of complex natural materials such as peptone. Liver extracts were strikingly stimulatory. Dark growth was improved by aeration and paralleled that in light. Darkgrown individuals were pale. Cultures accumulated a water-soluble sepia or almost black substance which was also produced by pale growths in the dark.With chemically defined media-the subject of this paper-it should be possible to explore systematically their ability to utilize high-molecular sources of energy and carbon, nitrogen and amino acids, biotin, thiamine, and cobalamin.To identify the growth requirements of aerobic phototrophs, culture methods are needed which combine adequate illumination with freedom from significant chemical contaminations. Such considerations apply with special force to these chrysomonads. Growing densely, they need much illumination. Hence they were cultured in shallow layers of medium, and their sensitive response to certain widely-distributed growth factors such as biotin and cobalamin spurred the development of methods to minimize the confusion introduced by * This investigation was aided by grants from the Lederle Laboratories Division of the American Cyanamid Company, the Atomic Energy Commission [contract AT(30-1)-863] and the Rockefeller Foundition. We are indebted to Doctors E. G . Pringsheim and R. A. Lewin for the geuerdus gift of cultures and unpublished information. Doctor F. C. Bersworth of the Bersworth Chemical Comp...

THE INFLUENCE OF THE MODE OF NUTRITION ON THE DIGESTIVE SYSTEM OF OCHROMONAS MALHAMENSIS

“…Autophagy was never observed in cells from 4 or 5 day cultures grown in Hutner's complete medium (24) . Autophagy appeared in cells kept for 24 hr in the starvation medium .…”

“…Cells grown in Hutner's complete medium (24) and subsequently starved for 16 or 24 hr contained lead phosphate reaction product in the vacuoles (v) (Fig . 3) and in the Golgi complex (gc) of most sectioned cells (Fig.…”

“…Ochromonas malhamensis was grown at 24-25°C in Hutner's medium (24) under conditions previously reported from this laboratory (28) . Under these conditions, the cells reached the end of the logarithmic growth phase after 150 hr .…”

“…Cultures for starvation studies were grown for 3 or 4 days in Hutner's medium (24), collected by centrifugation (36), and transferred to the starvation medium described by Myers and Graham for this organism (32), where they were maintained for 24 hr at 24-25°C at 50 footcandles of illumination from cool white fluorescent tubes . Escherichia coli was used for phagocytosis experiments .…”

“…The bacteria were grown in Difco nutrient broth (Difco Laboratories, Detroit, Mich .) at 25°C for [16][17][18][19][20][21][22][23][24] hr, centrifuged at 915 g for 15 min, washed with Ochromonas starvation medium, and added live to the Ochromonas cultures for 2 hr or heat-killed and added for 6, 16, or 22 hr before the cultures were harvested for experimentation . When the Ochromonas were subsequently harvested and washed, noningested bacteria remained in the supernatant and were discarded .…”