Chapter XIV — 171 — Relation of Marine Bacteria 



is an almost unexplored possibility. The fixation of nitrogen by Azoto- 

 bacter growing epiphytically on algae (Reinke, 1903; Keding, 1906) is 

 hardly true symbiosis because, while the algae may provide the bacteria 

 with a holdfast and organic nutrients, there is no evidence that the bac- 

 teria contribute fixed nitrogen to the algae, at least not until after the 

 death and decomposition of the bacteria. 



Marine plant pathogens : — Infections of marine plants by bacteria 

 have been reported. An interesting example is the disease of kelp known 

 as ''black rot" which was first noticed off the California coast by Brandt 

 (1923). It attacked the bladder kelp, Macrocyslis pyrifera, the elk kelp, 

 PelagopJiycus porra, and the ribbon kelp, Egregia laevigata. The causative 

 organism was kept in check by the colder water of winter and by proper 

 cutting of the kelp beds. 



Billet (1888a, b) isolated Bacterium laminariae and Bact. balbianii 

 from rotting kelp. Schaudinn (1903) described Bacillus sporonema, 

 which he isolated from rotting Ulva. Lagerheim (1900) presented evi- 

 dence that a fungus-like bacterium, which he named Sarcinastrum uro- 

 sporae, is responsible for gall formation on red algae. 



Cantacuzene (1930) found tumorous growths on Irish moss, Chrondus 

 crispus, which he attributed to infectious bacteria. Tumors or galls on 

 Saccorrhiza bulbosa were likewise found to be infected with bacteria. 

 Healthy plants could be experimentally infected by inoculating them with 

 the bacteria isolated from diseased plants. 



Large numbers of bacteria are associated with diseased eel grass, 

 Zostera marina, but they have not been proved to be pathogenic. After 

 finding Labyrinthula species in all specimens exhibiting symptoms, Renn 

 (1936) concluded that these fungi were the etiological agents of the 

 "wasting disease" of eel grass. HalopJiiobolus species (Barghoorn and 

 LiNDER, 1944) may also be involved. 



Nadson and Burg\\t:tz (1931) found several varieties of Torula and 

 other yeast-like organisms parasitizing Laminaria, Alaria, Fucus, and 

 other seaweeds. Several species of fungi parasitic on marine algae have 

 been described by Kibbe (1916), Zeller (1918), Sparrow (1934, 1936), 

 and others. Some of their observations are detailed in Chapter IX. 



Judging from the positive results that have been obtained from the 

 few precursory or exploratory observations made to date, it is believed 

 that pathogenic bacteria, yeasts, and mold fungi may extensively parasit- 

 ize seaweeds, diatoms, dinoflagellates, and other marine plants. This is a 

 most promising field for further investigation ; a field in which the results 

 may contribute to our knowledge of marine microbiology and general 

 hydrobiology. 



Although he regards the study of aquatic fungi as still being a virgin 

 field for research, Weston (1941) writes, "On the plant life of fresh water, 

 fungi are commonly, extensively and often destructively parasitic. Occa- 

 sional serious epidemics have been reported, chiefly on algae such as 

 diatoms, desmids or other plankton forms significant in aquatic ecology.' 

 Weston gives a resume of the ever-growing literature describing aquatic 

 fungi which have been found to be parasitic on fresh-water algae and 

 higher aquatic plants. The latter appear to be less susceptible to parasit- 

 ism than the simpler algae. He quotes Zopf to the effect that, "In the 

 household of nature the infectious diseases of the lower organisms play a 

 highly significant part." 



