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This paper is a report on the microbial flora of the waters and sediments of five lakes from the Canadian Subarctic, with special emphasis on the genus Cytophaga. The cytophagas are long, thin rods which are capable of flexing in liquids and of gliding motility on solid surfaces. They are important in the degradation and recycling of many relatively resistant, macromolecular polysaccharides and proteins such as cellulose, chitin, agar and keratin which occur as structural or storage residues of "higher" plants and animals in the natural environment. ... The samples were collected aseptically during the summer of 1971, flown to Edmonton and stored at 4 °C until processed, within two days of sampling time. ... Tests, which were carried out at the isolation temperature of each organism (10° or 25 °C), were as follows: C.C.A. [Cook's cytophaga agar] - growth, spreading, colour, length, width, shape and motility were described at 3-4 days (25 °C) or 5-6 days (10 °C); S.M.A. [skim milk acetate] - proteolysis (clearing) and silkiness of the liquid culture were noted at 2, 3 and 6 days and length, width, shape, flexing and motility observations were made at 10-14 hrs. and 2 days (25 °C) or 24-42 hrs. and 5 days (10 °C); S.M.A.-growth at 5° and 30 °C, and proteolysis were noted at 6 days. Gram stains and Munsell colour determinations were made at 4 days. ... The small number of samples used does not permit large-scale generalization; nevertheless some useful observations can be made. The three media and two temperatures used for isolation should screen the samples exhaustively for cytophagas (with the exception of any as yet unknown psychrophiles), as well as support the growth of various other micro-organisms. Very likely, other organisms could be found if a greater selection of media and conditions were used. The uniqueness of the microbial community of each site is noteworthy. The number and variety of bacterial types present varied widely. It is reasonable to conclude that those sites possessing a greater range of morphological types are likely to have a greater range of biochemical capacity in the degradation of organic molecules too. Of the total isolates 65% grew better at 30° than at 5 °C, 13% showed similar growth at both temperatures, and 16% showed no growth at 5 °C, whilst only 1% showed no growth at 30 °C, and 5% better growth at 5 °C than at 30 °C. The results for the Cytophaga cultures followed this trend, giving 61%, 13%, 15%, 4% and 6% respectively. This scarcity of psychrophiles should not be interpreted as necessarily reflecting the situation in the lakes, since the transit temperature and the temperatures of culture isolation were all higher than those in situ. The results do show a good potential for mesophilic growth if these areas were ever heated (by an oil pipeline for example), and turnover of materials could be expected to be fairly rapid. The genus Cytophaga, members of which spread by gliding motility on nutritionally weak media, were well represented in these lakes. ... Members of the genus Cytophaga, with their potential for waste polymer degradation, were recovered from all five lakes examined, and very large numbers were present in samples 4796 water and mud and 4810 water. ... The Cytophaga found in these subarctic lakes seem to differ very little from those present in more temperature regions of Canada.

A Microbiological Study of some Lake Waters and Sediments from the Mackenzie Valley with Special Reference to Cytophagas