( 1072 ) 
Other bacteria but the above named, producing a pigment from 
quereite, have not been found, neither by experiments with non- 
sporulating forms at higher temperatures nor among the microbes 
that remain alive in pasteurised materials. 
Finally it may be remarked that quereite (which is not susceptible of 
alcohol fermentation) is attacked, when no air is admitted, by fer- 
mentation bacteria of the Aërobacter-group, such as A. aërogenes, 
under production of carbonic acid, hydrogen, and of organic acids 
which have not yet been more exactly examined. 
3. Oxidation of Tyrosine to Melanine by Mierospira tyrosinatica. 
It is well known that the enzyme tyrosinase is able to oxidise 
tyrosine to a jet-black substance, which is formed at the air from 
dioxyphenyl acetic acid or homogentisinie acid. It is accepted that 
this substance originates after the formula *). 
ORE NO, oe Oe == CHN Be 
Tyrosine Homogentisinie acid 
In the experiments now to be treated I could not find ammonia 
which, according to the formula should come free, probably because 
all the nitrogen present in the tyrosine, is used for the growth 
of the bacteria. 
Hitherto this conversion had only been studied as a consequence 
of the action of an enzyme occurring in higher plants and also in 
higher Fungi. Nobody, however, had as yet described tyrosinase- 
producing bacteria, whose existence will be referred to in the next 
lines. As they are rather easily cultivated and are able to produce 
great quantities of the black pigment formed from tyrosine, which 
is identie with or closely allied to the melanines of the human body, 
they are of importance for experimental physiology. 
Tyrosine microbes are small vibrios, chiefly occurring in the sea 
and during the winter months present in the plankton. Fresh water 
is not however quite devoid of them and without much trouble 
they may be isolated from sewage water. The forms living in the 
sea produce, at least as regards the stronger varieties, besides tyrosinase, 
also tyrosine, and as this takes place from peptone they are to be 
recognised by the black stains which their colonies produce on 
broth-agar plates, which, as we have to deal here with inhabitants 
of the sea, should contain 3 proe. common salt. It is remarkable 
1) ABDERHALDEN, Physiolog. Chemie. 2te Aufl. p. 367, 1909. 
