The effect of bacteria on the solubilization of silica in diatom frustules

P atrick , S heila & H olding , A.J. 1985. The effect of bacteria on the solubilization of silica in diatom frustules. Journal of Applied Bacteriology 59 , 7–16.
Natural bacterial populations in samples of water from Loch Leven and Lough Neagh increased the rate of solubilization of frustule silica from an axenic Cyclotella meneghiniana culture, compared with sterile autolysis, at 25C. In the inoculated cultures 50–60% of the silica was solubilized over a period of 30 d. Bacterial populations in Loch Leven water also enhanced the solubilization of silica from non-axenic cultures of Asterionella formosa, Tabellaria flocculosa, Navicula pellicu-losa and C. meneghiniana , compared with control cultures sterilized with mercuric chloride. Similar results were obtained with Lough Neagh populations incubated with A. formosa . In comparison with untreated cells, the treatment of diatom cells with ultra-sonication did not increase the release of silica. Pure cultures of bacteria from Loch Leven water enhanced the release of silica from non-axenic A. formosa and axenic C. meneghiniana compared with sterile control treatments. The variation in the ability of cultures to solubilize the frustule silica appeared to be related to their potential to produce hydrolytic enzymes. Natural populations of Loch Leven and Lough Neagh water bacteria and certain bacterial cultures caused the diatoms to aggregate, which did not enhance the release of silica.