Study Of Bacteria And Fungi In Wool

Press, Volume C, Issue 29513, 13 May 1961, Page 7

Study Of Bacteria And Fungi In Wool

UR A. P. MULCOCK, “ 1 lecturer In the microbiology department at Canterbury Agricultural College, has gained a doctorate of philosophy in agricultural microbiology for his thesis on the studies he has made in the last six years into certain aspects of bacteria and fungi in the sheep’s fleece.

There are a good many records of bacteria of one sort and another in wool but they have usually been considered to be rather temporary contaminants of the fleece. Mr Mulcock has however, amply demonstrated in his studies that this is not so, and that in fact many types of bacteria and fungi spend their whole life cycle in the fleece of the sheep, where there are all the requirements for their growth. They derive their food from the sweat or suint and the break down products of the fibre.

The growth of micro, organisms is rarely retarded by temperature in the temperate zones but it may be considerably slowed down by either heat or cold. Close to the skin of the sheep temperature fluctuations are. however, slight owing to the constant temperature maintained by the animal which is sustained by the well recognised insulating properties of wool. Water is. however, often a limiting factor in their growth, but it has been found that micro-organisms have developed many special adaptations to allow them to contend with periods of drought, says Dr. Mulcock. Literature A survey of the literature on this subject as far back as 1898 has shown Dr. Mulcock that although much has been written about certain inhabitants of the fleece, and in particular Pseudomonas aeruginosa which produces the pigment pyocyanine causing green staining in wool, certain other aspects have been rather inadequately dealt with. “That so little attention has been paid to the microbiology of wool is not surprising since many of the most elementary facts concerning the composition, structure and formation of wool fibres have yet to be elucidated.” said Dr. Mulcock in his thesis. But he adds that “this state of affairs should be disturbing, at least, to those people who live in countries whose income is largely derived from the sale of wool, especially when the vast array of knowledge concerning the synthetic fibres tends to draw attention to defects associated with a natural fibre such as wool.” Dr. Mulcock has concentrated on two aspects of the microbiology of wool in particular. He has looked at the staining of the fleece by pigments produced by Pseudomonas aeruginosa already mentioned and a black discolouration of the tips of the fibres caused by the fungus Peyronellaea glomerata which has been recorded for the first time.

Studies of the first led in the laboratory to the development of an ingenious machine in which wool samples could be artificially stained by the pigment produced by the bacteria. This apparatus designed and built by Dr. Mulcock consisted of two refrigerator cabinets heated by infra-red chicken brooder lamps thermostatically con. trolled to less than a quarter degree variation from 33 degrees centigrade, the skin temperature level of the sheep. Samples of wool inoculated with the bacteria were suspended in a flask and subjected to recurrent deluges of water.

At the same time field studies were also initiated into a number of organisms in the fierce under various weather conditions. In a study of the longevity of the Pseudomonas bacterium it was found in a sample of green wool that this bacterium remained alive and viable between October 16. 1957 and March 17. 1959. when the experiment was discontinued. "No efficient explanation can be given for these results but the possibility that wool wax has some protective properties preventing the death of these bacteria cannot be discounted.” said Dr. Mulcock. “Unfortunately the work recorded here brings us no nearer the quantitative differentiation between susceptible type and immune type sheep, although some light has been shed on the reasons for the sporadic appearance of staining by Pseudomonas aeruginosa much requires to be done to elucidate finally all facets of the problem.” Towards the close of his thesis. Dr. Mulcock says that from the New Zealand farmer’s point of view both conditions studied are of great importance. The stain caused by pyocynine cannot be removed from the wool during normal scouring processes. This leads wool buyers to be suspicious of any wool showing discolouration, whatever its origin, lest the colouring substance be so firmly fixed to the fibre as to prevent its removal. Thus woolbuyers tend to discount discoloured wools from Id to 3d a lb, which taken over the whole New Zealand clip, can amount to some hundreds of thousands of pounds a year. No estimate, says Dr. Mulcock. can be made of the damage which may be caused by the fungus Peyronellaea glomerata, first detected in wool sent to Japan, until more accurate information about the extent of its occurrence is available. The damage caused by this organism is confined to the

tips of the fibres and it appears that the infected material is usually lost during scouring and carding so that in most instances wool prepared for spinning shows no evidence of the trouble as the black tips of wool have been broken off. Although break down of the tips of wool fibres is known to be caused by a number of factors, including ultra-violet light and mechanical abrasion, it appears from microscopical examination of wool fibres in which the fungus is growing that it is a major cause of the disintegration of the distal ends of the fibres, and even if one-eighth of an inch could be saved on each fibre this would amount to a worthwhile quantity of wool each season. The son of a Canterbury farmer, Dr. Mulcock was born in Christchurch and educated at Christ’s College and Canterbury College where he completed his master’s degree in botany in 1951. He joined the staff of Lincoln as a junior lecturer in microbiology, the same year. Dr Mulcock has served as chairman and secretary at the college branch of the Association of University Teachers.