ZoBell — 190 — Marine Microbiology 



After finding only from 20 to 625 aerobic and from none to 60 anaero- 

 bic bacteria per gram of fish tissue, Highlands and Williams (1944) 

 concluded that the chief hazard in the canning of sardines is in the hand- 

 ling and processing and not in the bacterial flora normally associated 

 with fish. The bacterial population increased rapidly during processing 

 preparatory to canning. The increase was related more to the nature of 

 the packing table surface than to any other single factor. Neither thermo- 

 tolerant nor thermophilic varieties were encountered. Halophilic bac- 

 teria were present only in low numbers. Eight per cent salt was required 

 to inhibit bacterial growth for a commercially practicable period of time. 



The spoilage of fish may be retarded or prevented by proper handling 

 tc minimize infection of the muscle tissue and by refrigeration. While 

 many bacteria associated with marine fish multiply slowly and are other- 

 wise biochemically active at temperatures ranging from 0° to — 5° C. 

 (Bedford, 1933a, h\ Gibbons, 1934c; Hess, 1934a, h), their proteolytic 

 activities are minimized by refrigeration at sub-zero temperatures. Fast- 

 freezing and storage of mackerel at — 28° C. was found by Kiser and 

 Beckwith (1942) to allay absolutely all bacterial activity. In fact, they 

 observed a decrease in the bacterial flora, including species of Achromo- 

 hacter and Micrococcus, in 15 days at — 20° C. Hess (1934a) reported 

 reductions of from 40 to 70 per cent in suspensions of marine bacteria 

 frozen in sea water for eight minutes at — 16° C, but all organisms were 

 not killed after 44 hours at this temperature. Some of the bacteria were 

 actively proteolytic at — 3° C. 



Griffiths (1937) reports a sharp rise in the bacterial population in 

 haddock flesh stored in ice. After 7 to 11 days, counts of 100,000 or more 

 bacteria per gram were found to indicate rapid subsequent decomposition. 

 Fish having 1,000,000 or more bacteria per gram were not considered to be 

 marketable. Griffiths emphasized the desirability of additional research 

 to establish bacteriological standards for acceptable quality of fish. 



Bacteria often affect the marketability of fish by causing discoloration, 

 Beckwith (1911) described Diplococcus gadidarum which caused the red- 

 dening of cod and allied fishes. Kellerman (191 5^) who called it Micro- 

 coccus gadidarum, isolated a similar red organism, Micrococcus litoralis, 

 from salted codfish. Klebahn (1919) found Micrococcus morrhuae, Sar- 

 cina morrhuae, and Bacterium halohium rubrum associated with reddened 

 dry cod. Gibbons (1937) found 30 species of halophilic bacteria, includ- 

 ing two species of Serraiia, associated with the reddening of salted fish. A 

 pink yeast, Torula wehmeri, along with Micrococcus albus-translucens, 

 Micrococcus lutulentus, and Bacterium zopfii were isolated from reddened 

 codfish by Hanzawa and Takeda (193 i). Clathrocystis roseo-persicina, 

 Oidium pulvunatum. Micrococcus roseus, Serratia salinaria, Vibrio halo- 

 bicus desulfuricans , and Torula epizoa have been credited with causing the 

 discoloration of codfish, according to Tanner (1944). 



The greenish-yellow discoloration of halibut was attributed primarily 

 to Pseudomonas fluorescens by Harrison (1929), who also isolated from 

 halibut Flavobacterium marinum, Fl. balustinum, Fl. fucatum, Fl. mariy 

 and Achromobacter pellucidum. Bedford (1933a) attributed the discolor- 

 ation and subsequent souring of halibut to the activity of various pink, 

 orange, and yellow marine bacteria, in addition to the fresh-water Ps. 

 fluorescens. All of the bacteria were active at 0° C, and some developed 

 at - 5° C. 



