Antibacterial Activity of Extracts
Obtained from Blue-Green Algae
FLOYD F. DAVIDSON, Professor of Biology
Department of Biology
Baylor University
Waco, Texas
During the past 85 years interest in the Cyanophyta from the standpoint
of their adverse effects on water supply and sewage disposal has increased
among biologists and sanitary engineers. These effects are indicated not only
by changes in appearance, color, and taste of the water, but also by changes
in other aquatic organisms. Even more important are the varying degrees of
reactions in humans and other animals which ingest or come in contact with
water containing high concentrations of toxic blue-gree algae.
Since the reported occurrence of a toxic water bloom of NodutaHa spumi-
geria from southern Australia (1), about 50 outbreaks of algal poisoning in
wild and domestic animals have been reported. Epidemic intestinal disorders
involving thousands of people have been also attributed to blue-green algae.
Doubtless other outbreaks of algal poisoning have been neither studied nor re -
ported.
Six genera of Cyanophyta have long been known to possess species which
are  toxic  to  Wild  and  domestic  animals:       Microcystis,   Anabaena,     Aphani-
zomenon,   Nodularia,   Gloeotrichia,      and  Coelosphaerium.      Two of these gen-
era,   Microcystis and Anabaena, and certain members of the subgroup Oscil-
latoriaceae (2,3)  have been implicated in human reactions.
In a previous paper (4) we reported the occurrence of a toxic waterbloom
of Nostoc rivulare Kutz. in central Texas. Not only is this the first reported
incident of algal poisoning involving the genus Nostoc, but it is also the only
such outbreak reported from the southwest U. S. Even more signifie ant
are the unusual reactions evoked by the algae inlaboratory and field animals.
Wild and domestic animals, including fish, frogs, chickens, ducks,turkeys,
and cattle, that drank the algae-infested water died within a few hours or became acutely ill. In laboratory tests, intraperitoneal injections of albino
mice with lethal doses of algal material ur with extracts prepared from preserved material produced symptoms characteristic of algal poisoning: restlessness, paralysis of hindquarters, renal and intestinal disorders; increase in
respiratory rate; decrease in blood sugar, blood coagulation time, red blood
cell count, rate of heartbeat; death. Subcutaneous injections resulted in
complete necrosis of the abdominal wall, including the skin. Mice receiving
sublethal injections developed tumors on the shoulders; two experienced evisceration; the eye of one completely atrophied. Bacterial associates of Nostoc
rivulare were nontoxic to the mice.
Antibacterial substances obtained from certain Cyanophyta have been
studied by several investigators. It has been reported that Microcystis
aeruginosa Kutz. possesses some antibacterial properties against certain bacteria (5, 6), and that Oscillatoria splendida Grew secretes a volatile substance
which kills its bacterial associates and other micro-organisms in the algal
culture (7). A substance which inhibits pigment formation in Serratia
marcescens Bizio has been obtained from certain species of Cyanophyta (4).