Ecological studies on algal‐lysing bacteria in fresh waters

Abstract

Algal-iysing bacteria are present in five lochs, two reservoirs, one sewage works and five alkaline soils whieh were examined. Nine out of thirty-six isolates have been studied in detail and all are gram-negative non-fruiting myxobaeteria. All are aerophilic, require a neutral or alkaline pH (optimum 7-0-9 0) for good growth, have temperature optima of 28-37 "C, require contact with the host for lysis to oecur, and are so similar in morphology and host range that they all appear to be strains of a single genus. They lyse all bloom-forming Cyanophyeeae on whieh they have been tested, including species of Anabaena, Aphanizomenon, Gloeotrichia, Microcystis and Oscillatoria. Their abundance is usually correlated direetly with the abundance of Cyanophyeeae in eutrophic waters and it is probable that in most ecosystems the algae and the bacteria co-exist, although if the equilibrium changes markedly as a result of change in environmental conditions situations may arise where the bacteria may play an important role in the lysis of algal blooms. The available evidence suggests, however, that this is likely to be a rare occurrence in natural ecosystems.Ecological studies on algal-lysing bacteria in fresh waters 579 Materials and MethodsHabitats studied Eight fresh waters in Scotland (Balgavies Loch, Long Loch, Loch of Lindores, Monikie Reservoir and Thriepley Loch), England (Esthwaite Water and Loweswater) and Wales (Eglwys Nunydd Reservoir) were surveyed for the presence of iytic bacteria. These habitats are detailed in Table 1. The four Scottish lochs are mesotrophic or eutrophic, are dominated by species of Anabaena, Aphanizomenon, Microcystis and Asterionella and are used for angling and recreational sports. The waterworks at Monikie belong to the East of Scotland Water Board and the slow sand filters often develop a succession of algae during the summer in which some, or all of Gloeotrichia echintdata, Microcystis aeruginosa, Aphanizomenon flos-aquae and Anabaena circinalis predominate. Eglwys Nunydd Reservoir, in Wales, provides water for the British Steel Corporation strip mills at Port Talbot. Its flora is usually dominated in summer by Microcystis. Esthwaite Water and Loweswater are eutrophic waters in the English Lake District, and were sampled only once (6 October, 1971) for the presence of algal-lysing bacteria. During this sampling period Microcystis was present in Esthwaite Water and Gomphosphaeria and Anabaena were present in Loweswater. The sewage works at Forfar, Angus (Nat. Grid. Ref. NO 443502), which is of the trickling filter type, and various soils in the vicinity of Dundee were also sampled.

The isolation and identification of predatory bacteria from a Microcystis algal bloom

“…A chloroform test was carried out to test whether the plaque developments were either caused by bacteria or cyanophages (Daft et al, 1975;Tucker and Pollard, 2004). An aliquot (10 m ) of dam water was mixed with 0.5 m of chloroform and vortex mixed for 5 min.…”

“…No plaques were observed in the dam water samples treated with chloroform (Figures 1b and d). Chloroform is a chemical that is known to destroy cyanophages (a virus that specifically attack cyanobacteria) but not bacteria or cyanobacteria (Daft et al, 1975;Tucker and Pollard, 2004). Thus in the treated samples, all the cyanophages had been destroyed by the chloroform that was added hence the growth of Microcystis spreading and forming a lawn with no plaques.…”

“…The assumption was made that the plaques originated from a single bacterium (Daft et al, 1975;Bird and Rashidan, 2001) and this cyanophage activity test was done to confirm the assumption. Thus the next study objective was to identify which bacteria was preying upon the cyanobacteria and in the same process create plaques.…”

“…These microbial agents may play a major role in the prevention, regulation and termination of harmful algal blooms. In many cases, these bacterial agents are species-or genus-specific (Bird and Rashidan, 2001), while others attack a variety of cyanobacteria classes (Daft et al, 1975). The biological control method will complement other strategies such as an integrated biological water management plan that have been proposed for the dam (Harding et al, 2004).…”

A Study on the Lysis of a Bluegreen Alga Anabaena cylindrica by a Bacterium

“…(Baldi et al 1997;Hannen et al 1999). 자연 생태계에서 수중 미생물은 남조류의 생장과 비례적으로 생장하는 것으로 알려져 있는 데 (Mitsutani et al 1987;Daft et al 1975;Stewart and Daft 1977) …”