114 CUEMJt^TRY OF RACTERIA A\D THEIR PRODUCTS 



upon enzyme action, just as with lii<i:lier cells. Liquefaction of 

 jielatiu is a familiar example of the enzyme action of bacteria; and 

 since the filtered cultures of liquefactive bacteria are also capable 

 of digestintj: gelatin, tlie enzymes are evidently excreted from the 

 cells. Dead baeteria, killed by thymol or by other antiseptics that 

 do not destroy proteolytic enzymes, will also digest gelatin. Numer- 

 ous investigations have established the wide-spread occurrence of 

 many soluble enzymes both in bacteria and in their secretions, indi- 

 cating that bacterial cells are as dependent on enzymes for the pro- 

 duction of their metabolic activities as are higher types of cells, and 

 that these enzymes are not onlj- present as intracellular constituents, 

 but that they also escape from the cells. Even the spores may con- 

 tain active enzymes.^* A striking property of bacteria is their re- 

 ducing power, whicii has led to the introduction of selenium and 

 tellurium salts, which are reduced to the metals, as an index of bac- 

 terial life and activity (Gosio). 



The diffusion method of Wijsman, or, as it is more frequently 

 called, auxanographic method of Beijerinck, offers a relatively simple 

 )neans of detecting the presence of extracellular bacterial enzymes. 

 Eijkman^"^ in particular has used this method, which consists of mix- 

 ing agar with milk, or starch, or whatever material is to serve as the 

 indicator of the enzyme action ; the agar is then inoculated with bac- 

 teria and plated (or else the bacteria are inoculated as a streak on 

 the surface of the agar). About each colony there will appear a 

 zone of clearing in the medium, if it produces enzymes digesting 

 the admixed substance. By this means Eijkman found that all bac- 

 teria that produce enzymes digesting gelatin also digest casein, and 

 those that do not digest gelatin are equally without effect on casein ; 

 therefore, it is probably the same enzyme that digests both. As the 

 hemolytic action of bacteria is not constantly related to their gelatin- 

 dissolving i)ropei'ty, the hemolysis probably is produced by other 

 means than the proteolytic enzymes.''" A few pathogenic bacteria 

 (anthrax, cholera) digest starch, and B. pyocyaneus, Staphylococcus 

 pyogenes aureus, and B. prodigiosus all produce fat-splitting enzymes 

 demonstrable by this method. B. pyocyaneus, Eijkman found, di- 

 gested elastic tissue readily,''' as also did a bat-illus i-cseinbling B. 

 suhtiiis obtained from the tissue of a gangreiious lung. The following 

 table by Buxton ''^ gives an idea of the disti-ihution of enzymes in 

 bacterial secretions as determined by the auxanographic method : 



•'<4 EfTront, Mon. sc. Quesnevillc I!i(i7, j). Sl. 



35 Cent. f. Biikt., 1001 (20), S4 1 . 



3« Sec .Jordan. Biol. Stiulicy 1)\ iIil' |.u|>i!s of W. T. Sod^^wick. r.KMI. p. IJ). 



37 (Vnl. f. Hakl.. 1 !»(»:! (:(.-,). 'l . 



3« Aiiicricaii .Med., l!l(i:{ ( (l ) . i:i7. 



