52 



HOPJXESS IN WATTLE BARK INFUSIONS. 



By R. Greig-S-mith, D.Sc, Macleay Bacteriologist to the Society. 



(With Plate ix.) 



The development of i-opiness in tan liquors is oeeasionally met with and \n-o- 

 Ijably would be of more conunon occurrence but for the fact that tanners have 

 learnt by experience how to treat their liquors in order to avoid this objectionable 

 fermentation. The phenomenon does not appear to have been examined, or at 

 least no information about such rojiiness has been published. Doubtless the rea- 

 son for this lies in the difficulty of isolating an organism, capable of producing 

 ropiness, from such a population of diverse organisms as must be present in a 

 fluid with the history of tan. liquor. But, beyond this fact, there is something 

 about the subject that is peculiar, as was shown before this investigation was 

 begun. A tan li(|uor claimed to be ropy was sent to the laboratory and upon 

 being examined no ropiness could be detected. It was (uiite limpid and, upon 

 being tested for viscosity, showed a water ratio of 1.0714 at 19°. When allowed 

 to flow through a tine capillary, 100 e.e. of the reputed ropy liquor ran through 

 in 210 seconds as against 196 seconds for distilled water. The liquid was plated 

 and the bacteria examined, but no ropy organisms could be detected. 



The Isolation of the Bacteria. 



On account of the diversity of the tan liquor fliu'a and the difficulty of ob- 

 taining a good specimen of ropy liquor at the time, the writer considered that the 

 ]>roblem could best be attacked from the side of the wattle bark. There promised 

 to be more chance of obtaining an organism capable of causing the ropy fermen- 

 tation of raw bark infusions than of isolating a similar organism from a ropy 

 tan liquor. As a matter of fact, during some experimental work, ropiness did de- 

 velop in a bark infusion and a search showed, among many colonies, one pos- 

 sessing a ropy consistency upon a plate of dextrose medium. The organism 

 also caused a fluid medium containing dextrose to become ropy. It was reserved 

 until occasion permitted its further examination . 



Some months later, it was decided to isolate fresh races of the ropy organism. 

 FragTiients of wattle bark (Acacia p/ionnitha) were jiut into boltles and covercil 

 with water and sometimes with nutrient li(|uids. Two bottles out of many showed 

 ropiness. One of them had received raw tap water, the other boiled tap water 

 with 0.25 % meat-extract. It was evident that the bacterium was to be found 

 in the bark and was not derived from an outside source such as the tap water and, 

 from the great number of bottles that were prepared, it was shown that the 

 liacteria were not to be found on every bit of bark. A further test as to the 

 .absence of the bacteria in tap water was made by filtering a (piantity of water 

 and using the sli'ne that adhered to the candle in conjunction with sterilised and 

 raw baiks. No ro]iiness developed in either case. 



