Publication Date:
2020-07-30
Description:
Bacterial epiphytes of Gracilaria conferta were quantified. Saprophytic bacteria reached 350 times and agar degraders 25000 times higher numbers g-1 algal wet wt on tissues infected with the 'white tips disease', as compared to healthy tissues. A bacterial inducing agent of the 'white tips disease' was detected. Addition of 10(2) to 10(3) cells of this isolate ml-1 medium led to increased rates of infection. This effect did not occur if the isolate was autoclaved before addition. The virulent bacteria could always be isolated from infected tissues. It frequently, but not always, infected G. conferta and should be regarded as a facultative parasite. Several factors influenced the disease development. Temperatures above 20-degrees-C, in combination with photon flux densities of more than 200 muE m-2 s-1, increased the rate of infection. Relatively low amounts (more than 25 mug ml-1) of certain organic nutrients (peptone and yeast extract) led to strong manifestations of the disease. Addition of agar did not cause any symptoms, while 5 mg l-1 of the antibiotic rifampicin prevented the alga from being infected.
Type:
Article
,
PeerReviewed
Format:
text
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