CULTURAL CHARACTERS. GROWTH REQUIREMENTS 791 



is relatively thermolabile ; it is inactivated by heating to 120° C!. for 30 minutes. 

 Both substances are present in blood. The label " X factor "-is generally applied 

 to the substance present in blood pigments, the label " V factor " to the relatively 

 thermolabile substance provided by animal or vegetable tissues or by most bacterial 

 cells (see also Thjetta 1921, Thjotta and Avery 1921, Davis 1921, Fildes 1922, 

 1923, 1924, Kristensen 1922, Valentine and Rivers 1927). 



Pittman (1935) brought evidence to show that V factor was closely concerned 

 in oxidation-reduction processes of the growing cell. With regard to X factor, 

 early observations (Olsen 1920, Fildes 1921) suggested that its growth-promoting 

 activity was correlated with its ability to act as a peroxidase ; but not all peroxides 

 promote the growth of//. influenzcE, and certain iron compounds without peroxidase 

 activity will act as X factor (Baudisch 1932). All such iron compounds that have 

 been tested in this respect have shown catalase activity (see Davis 1921, Webster 

 and Baudisch 1925, Bourn 1927, Baudisch 1932, Knight 1936). H. influenzce 

 grows poorly under anaerobic conditions, but Kopp (1927-28), Eirund (1929) and 

 Anderson (1931) have recorded the anaerobic growth of certain strains. In these 

 conditions, the organism grows in the absence of X factor. These facts together 

 suggest that X factor is closely associated with the aerobic respiration of the 

 bacillus. 



It is now apparent from the work of the Lwoffs (Lwoff and Lwoff 1937o, 6, c) 

 that V factor is one of two co-dehydrogenases, di- and tri-phospopyridine nucleotide 

 (see Chapter 3), and that the X factor is hsemin, which, they conclude, is normally 

 utilized by H. zVi^wejizoefor synthesis of cytochrome, cytochrome -oxidase, catalase 

 and peroxidase. 



These observations clearly provide an explanation of the satellitism described 

 by Grassberger. The staphylococci, and many other organisms of greater synthetic 

 ability than the hsemophilic bacilli, synthesize the co-dehydrogenase, which diffuses 

 into the medium and stimulates the growth of bacilli that require it. They explain, 

 too, the anaerobic growth of H. inflnenzce without the help of X factor, since in the 

 absence of molecular oxygen there is no need for that part of the cytochrome 

 system which protects the organism against the inhibitory effect of oxygen (see 

 Chapter 3). 



It should be noted that Hoagland and his colleagues (1942) have found in 

 blood an unidentified factor which stimulates the growth of H. vnfliienzcB in the 

 presence of optimum amounts of X and V factors. 



Among the species included within this genus, besides H. influenzce itself, are 

 (1) the bacillus associated with conjunctivitis, described by Koch (1887) and 

 Weeks (1887), and commonly known as the " Koch-Weeks bacillus " ; (2) the 

 bacillus isolated by Friedberger (1903) from the prepuce of dogs, named by him 

 B. hcemoghbinopliilus canis and now known as H. canis ; (3) the organism isolated 

 by Shope (1931) (see also Lewis and Shope 1931) from swine influenza and named 

 by him H. influenzce-suis ; (4) the causative organism of whooping cough, described 

 by Bordet and Gengou (1906) and named by them B. pertussis, now known as 

 //. pertussis ; (5) the causative organism of soft sore described by Ducrey as the 

 probable cause of soft chancre (see Chapter 79) and named //. ducreyi by LwofiF 

 and his colleagues (Lwoff and Pirosky 1937, Lwoft" 1939) ; (6) the bacilli described 

 by Rivers (1922a) as H. para-influenzce, associated with acute pharyngitis and 

 bacterial endocarditis in man ; and (7) the causative organism of broncho-pneumonia 

 in rodents and dogs, described by Ferry (1912-13) as B. bronchisepticus and now 



