THE VENEZUELAN SALT-FISH INDUSTRIES 



to 28 percent. Cultures that had flourished in low salt concentration media, which had 

 then been allowed to stand a long time to dry out, yielded inoculums capable of growing 

 in a wider range of salt concentrations than transfers from young vegetative colonies. 



The apparent ability of certain strains of the organism to grow profusely in high con- 

 centrations of salt, as shown by other investigators (Harrison and Kennedy, 1922; and Stuart, 

 1940b) may be due to repeated propagation in media of high salt content. In this connec- " 

 tion, Rubenchick (1936), having found bacteria that changed their habits from halophobic 

 to halophilic, reached the conclusion that the classification of bacteria on the basis of 

 their behavior in various concentrations of sodium chloride is misleading. 



On the other hand, Stuart (1940a) found that bacteria grown in media having a sodium 

 chloride concentration greater than 3 molar (about 17 percent) are materially affected by 

 protein concentration. The addition of small quantities of cysteine to the media stimu- 

 lated the growth of halophilic bacteria. This effect was especially marked in media in 

 which the salt concentrations were from 3 to 3.8 molar (roughly 17 to 22 percent) and the 

 pH values from 6.6 to 7 02. 



Other factors, too, may influence the growth of the reddening bacteria in salted fish. 

 The enzymes present in the raw substrata, or more likely, the microflora encountered in 

 the natural environment, may contribute to the ease with which the reddening organism es- 

 tablishes and maintains itself in the salteries even in contact with saturated brine or 

 solid salt. 



Temperature Relations 



At the prevailing room temperatures of 25° to 30° C, the organism was found to grow 

 well and to show more pronounced coloration than at 37° or 42° C. However, growth was also 

 good at the latter temperatures. No growth was observed at either 4° or 55° C. 



Relation to Free Oxygen 



In infected salteries it is often observed that the red organisms will grow profusely 

 at the surface of a tank containing brine-salted fish, but that at a short distance down 

 there is little evidence of their presence. As a lead to a possible method of control, 

 it was thought advisable to determine whether or not the reddening bacteria could live with- 

 out oxygen. 



Accordingly, tubes of agar media, containing glucose and 5 percent salt, were inocu- 

 lated heavily while in fluid condition at 45° C. After incubation at 42° C a pink ring or 

 pellicle developed on the surface of the medium. No growth was observed in the interior. 



Bucher's anaerobic method also indicated that the organism was a strict aerobe. In- 

 oculated dextrose-formate agar tubes were placed inside larger tubes containing at the bot- 

 tom 4 grams of pyrogallol plus 10 cubic centimeters of 10 percent sodium hydroxide solution. 

 The larger tubes were then tightly stoppered. No gromrth was observed after several days 

 incubation. 



According to a study by Stuart (1940b) the growth of red chromogenic, halophilic bac- 

 teria appears to be stijnulated by a slight reduction of the oxygen tension. It was sug- 

 gested that the tendency of these organisms to be strictly surface growers might be a sur- 

 face tension phenomenon. 



Liquefaction of Gelatin 



The reddening organism from both the pink and the cherry-red cultures was inoculated 

 into tubes of 10 percent plain and nutrient gelation containing 5 percent salt. Good growth 

 was noticeable in both types of gelatin after 24 hours incubation. After two days incuba- 

 tion, the tubes were cooled in the refrigerator for two hours. All the cultures gelled, 

 showing that much of the gelatin had not yet been transformed. Inoculated tubes containing 

 the gelatin media of either type would not re-solidify after incubation for 15 days, al- 

 though the cultures were in the refrigerator for twenty hours. Control tubes did solidify 



70 



