Occasional pathogenic bacteria promoting ice-ice disease in the carrageenan-producing red algae Kappaphycus alvarezii and Eucheuma denticulatum (Solieriaceae, Gigartinales, Rhodophyta)

Abstract

The bacterial isolates from normal and diseased branches of Kappaphycus alvarezii and Eucheuma denticulatum in the Philippines were examined for possible role in the development of the ice-ice disease. The numbers of bacteria on and in ice-iced branches were 10-100 times greater than those from normal, healthy ones. Grampositive bacteria predominated in almost all branch sources, but with an increasing proportion of agar-lysing bacteria in branches suffering from the ice-ice disease. These agar-lysing bacteria were composed of yellow and non-pigmented, spreading colonies identified to the Cytophaga-Flavobacterium complex and the Vibrio group. Among isolates which mainly appeared on ice-iced branches, two strains, designated as P11 (Vibrio sp.) and P25 (Cytophage sp.), which showed pathogenic activity, were obtained. These strains caused early ice-ice whitening of K. alvarezii especially when subjecting branches to environmental stress, such as reduced salinity and light intensity, suggesting that these bacteria were occasionally pathogenic. This paper offers new evidence of bacterial role in the development of so-called ice-ice disease among farmed species of Kappaphycus.

Pathogen-Induced Defense and Innate Immunity in Macroalgae

“…(as Gracilaria conferta) were capable of degrading its agar cell wall matrix (Weinberger et al, 1994). Similar observations have been reported for other red macroalgae (Largo et al, 1995;Jaffray et al, 1997), as well as for kelps (Lin et al, 2004). Degraders of phycocolloids are usually rare in nonalgal environmental samples (for this reason agar is traditionally used for the gellification of microbiological media), which indicates that their concentration on macroalgae has coevolutionary reasons.…”

Investigation of the role of a β(1–4) agarase produced by Pseudoalteromonas gracilis B9 in eliciting disease symptoms in the red alga Gracilaria gracilis

“…Of the epiphytic bacteria tested, a positive correlation between an agarolytic phenotype and bacterial pathogenicity was discovered (Jaffray & Coyne, 1996). Other than the aforementioned example, four other incidences of disease, namely 'ice-ice' white powdery disease in Eucheuma and Kappaphycus species, the disease in the red alga Rhodella retriculata, the 'rotten-thallus' syndrome in a Gracilaria species and the 'white-tip disease' of Gracilaria conferta, were all attributed to agarolytic bacteria (Friedlander & Gunkel, 1992;Largo et al, 1995;Lavilla-Pitogo, 1992;Toncheva-Panova & Ivanova, 1997). However, the role of the agarases in the virulence mechanism of these bacterial pathogens was only hypothesized.…”

Rotten thallus of Red Seaweed, Gracilariopsis heteroclada Zhang et Xia, is Associated with Agar-Digesting Bacillus spp

“…These were identified as agar-digesting bacteria, which were also isolated from diseased Kappaphycus alvarezii and Eucheuma denticulatum (Largo et al, 1995) and Gracilaria spp. (Lavilla-Pitogo, 1992;Martinez & Padilla, 2016) from previous studies.…”

“…and Vibrio sp. in Kappaphycus alvarezii and Eucheuma denticulatum (Largo, 2002;Largo, Fukami, & Nishijima, 1995). Agar-digesting bacteria have the ability to degrade seaweed agar by forming a depression around the colony and/or liquefy the agar (Goresline, 1931;Stanier, 1941).…”