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. 2022 Dec 22:13:1091561.
doi: 10.3389/fmicb.2022.1091561. eCollection 2022.

Isolation and characterization of a high-efficiency algicidal bacterium Pseudoalteromonas sp. LD-B6 against the harmful dinoflagellate Noctiluca scintillans

Junyue Wang  1   2 , Xueyao Yin  1   2 , Mingyang Xu  1   2 , Yifan Chen  1   2 , Nanjing Ji  1   2 , Haifeng Gu  3 , Yuefeng Cai  1   2 , Xin Shen  1   2
Affiliations

Isolation and characterization of a high-efficiency algicidal bacterium Pseudoalteromonas sp. LD-B6 against the harmful dinoflagellate Noctiluca scintillans

Junyue Wang et al. Front Microbiol. .

Abstract

The dinoflagellate Noctiluca scintillans is a harmful algal species that is globally distributed and poses a certain threat to marine ecosystems. Recent research has shown that the application of algicidal bacteria is a promising method to prevent and control such harmful algal blooms (HABs), given its advantages of safety and efficiency. In this study, a strain of algicidal bacterium LD-B6 with high efficiency against N. scintillans was isolated from the coastal waters of Lianyungang, China. 16S rDNA sequence analysis showed that the strain LD-B6 belongs to the genus Pseudoalteromonas. Furthermore, the algicidal effect of LD-B6 on N. scintillans was investigated. The results showed that strain LD-B6 exerted strong algicidal activity against N. scintillans. After 12 h of bacterial culture addition to algal cultures at a 2% final volume rate, the algicidal activity reached 90.5%, and the algicidal activity of LD-B6 was influenced by the density of N. scintillans. In addition, the algicidal bacterium LD-B6 was found to indirectly lyse algal cells by secreting extracellular compounds. These algicidal compounds were stable, indicating that they are not proteins. Importantly, strain LD-B6 was broadly general, showing varying degrees of lysing effects against five of the six algal species tested. On the basis of the described studies above, the algicidal powder was also initially developed. In summary, the isolated bacterial strain LD-B6 shows the potent algicidal capability to serve as a candidate algicidal bacterium against N. scintillans blooms.

Keywords: Noctiluca scintillans; Pseudoalteromonas; algicidal activity; algicidal bacteria; harmful algal bloom.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling editor declared a past collaboration with the author HG.

Figures

FIGURE 1
FIGURE 1
Microscope images of Noctiluca scintillans when co-incubated with strain LD-B6 at (A) 0 h, (B) 12 h. Scale bars = 100 μm.
FIGURE 2
FIGURE 2
Phylogenetic tree of algicidal bacterial strain LD-B6 based on 16S rDNA sequence. Support of nodes > 50% is shown. Bar 0.05 means a nucleotide substitution rate of 0.05.
FIGURE 3
FIGURE 3
Algicidal activities of different concentrations of LD-B6 culture on Noctiluca scintillans based on (A) algal cell concentration and (B) algicidal activity. The error bars represent standard deviations (n = 3).
FIGURE 4
FIGURE 4
Algicidal effect of strain LD-B6 at different Noctiluca scintillans initial cell densities. The error bars represent standard deviations (n = 3).
FIGURE 5
FIGURE 5
Algicidal activities of different fractions of LD-B6 culture on Noctiluca scintillans based on (A) algal cell concentration and (B) algicidal activity. The error bars represent standard deviations (n = 3).
FIGURE 6
FIGURE 6
Algicidal effect of strain LD-B6 cell-free supernatant at different temperatures (A), pH (B) conditions, and repeated freeze-thaw (C) treatment against Noctiluca scintillans. The error bars represent standard deviations (n = 3). Different letters a, b represent significant differences between groups (p < 0.05).
FIGURE 7
FIGURE 7
Algicidal activity of bacterial strain LD-B6 on representative HABs species. N.s, Noctiluca scintillans; H.a, Heterosigma akashiwo; P.m, Prorocentrum micans; S.c, Skeletonema costatum; G.i, Gymnodinium impudicum; H.s, Heterocapsa steinii. The error bars represent standard deviations (n = 3).
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