ZoBell — 196 — Marine Microbiology 



and LiNDER (1944) have investigated the physiology of several such fungi. 

 According to Imshenetsky and Kokurina (1941), microorganisms cause 

 the destruction of jute coverings on ships. 



Bacterial deterioration of cork and rubber : — Cork is a ligno-cellulose- 

 suberin complex filled with air spaces which are responsible for its buoy- 

 ancy. Large quantities of cork are used for floats on fish nets, fish lines, 

 life preservers, etc. Although relatively resistant to bacterial attack, 

 cork is decomposed by marine microorganisms which slowly destroy its 

 buoyancy by rupturing the cell walls of the cork. Eventually, pieces of 

 cork continuously or periodically exposed to sea water break to pieces. 



Rubber is generally regarded as being biologically inert, but highly 

 purified rubber, both natural and synthetic, as well as various rubber 

 products, are susceptible to bacterial oxidation in the presence of minerals 

 and moisture. Even the small areas of rubber gasket exposed to water in 

 citrate of magnesia bottles filled with sea water causes the consumption 

 of oxygen as the rubber is oxidized by bacteria. 



According to ZoBell and Beckwith (1944), rubber is attacked by 

 many marine bacteria, including species of Actinomyces, Mycobacterium, 

 Micrococcus, Micromonospora, Nocardia, Pseudomonas, and Bacillus. This 

 is not particularly surprising when it is recalled that rubber is an unsatu- 

 rated hydrocarbon having the composition (C6H8)n. Unsaturated hydro- 

 carbons are quite susceptible to bacterial oxidation. Synthetic rubbers 

 are closely related chemically to natural rubber. Some of the synthetic 

 rubbers are more readily oxidized by bacteria than is natural rubber. 



Rubber products are prepared by compounding vulcanizing agents, 

 accelerators of vulcanization, antioxidants, softeners, fillers, etc., with 

 rubber hydrocarbon. Manufacturers have devoted little attention to the 

 development of antimicrobial agents for rubber products, for the obvious 

 reason that they have been more concerned with wearing qualities, heat- 

 resistance, tensile strength, elasticity, vulcanizability, and other proper- 

 ties than with biological inertness. Only when it is continuously in con- 

 tact with moisture does the bacterial deterioration of rubber become a 

 practical problem. Most rubber products, including hoses, bumpers, rub- 

 berized products, certain chlorinated rubber paints, bearings, etc., used 

 at sea are either submerged or subject to frequent wetting with sea water. 

 For such rubber products the development of antimicrobial qualities may 

 be desirable. 



Halophilic bacteria in solar salt : — Typical marine bacteria are hardly 

 halophilic since very few of them grow well in media containing more than 

 5 per cent salt. However, a small percentage of the bacteria in the sea are 

 able to grow in saturated salt solutions. Such organisms are particularly 

 abundant in marine salterns where halophilic chromogens often impart a 

 red color to the brine and crude salt. Pelrce (1914) regarded red chromo- 

 genic bacteria as being the principal cause of the pink to red coloration of 

 San Francisco Bay salterns, although the algae, Protococcus salinus and 

 Dunaliella salina, may be partly responsible. Peirce did not identify the 

 bacteria. They were obligate halophiles, growing in concentrated brine 

 but not in diluted brines. The bacteria grew on salt codfish, giving it a 

 red color. 



Unless measures are taken to sterilize re-crystallized and purified 

 solar salt, it may carry halophilic bacteria which are instrumental in the 



