Dechlorination effects of Aroclor 1254 by <i>Anabaena</i> PD-1 cells.

<p>The result was presented as the mean values of quadruplicate experiments (**<i>P</i><0.01, *<i>P</i><0.05; ‘a’ indicates group II, III, IV vs. the control group I; ‘b’ indicates group III, IV vs. group II).</p

The biodegradation percentage of dioxin-like PCBs degraded by <i>Anabaena</i> PD-1 for 7 days.

<p>The total initial exposure concentration for dioxin-like PCBs is 2 mg/L. The result was presented as the mean values of quadruplicate experiments.</p

Primers used for the quantitative real-time polymerase chain reaction in this study.

a<p>Primers with accession numbers belong to a gene cluster. Primers without accession numbers were designed according to the reference <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091162#pone.0091162-Kaneko1" target="_blank">[35]</a>.</p

Comparison of induced proteins by (chlorinated) aromatic compounds in <i>Anabaena</i> PD-1 and other microorganisms.

<p>Comparison of induced proteins by (chlorinated) aromatic compounds in <i>Anabaena</i> PD-1 and other microorganisms.</p

Gene expression levels in control and PCB-treated groups.

<p>Expression levels of genes encoding for (a) dioxygenase, (b) cytochrome b6f Fe-S protein, (c) ABC transporter substrate-binding protein, (d) porin, (e) enloase, (f) fraH, (g) malate-CoA ligase, and (h) methanol dehydrogenase. Data represented the mean ± SD, and significant difference from the control group was determined by *<i>p</i><0.05 and **<i>p</i><0.01.</p

The changes of chlorophyll <i>a</i> in cells of cyanobacterium <i>Anabaena</i> PD-1 exposed to different concentrations of Aroclor 1254.

<p>The result was presented as the mean values of quadruplicate experiments (**<i>P</i><0.01, *<i>P</i><0.05; ‘a’ indicates group II, III, IV vs. the control group I).</p

Hypothetic scheme of PCB degradation by Anabaena PD-1.

<p>Numbers in brackets present the different proteins in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091162#pone-0091162-t002" target="_blank">Table 2</a>.</p

Upregulated proteins of <i>Anabaena</i> PD-1 exposed to Aroclor 1254 for 30 d.

<p>0409-ABC transporter substrate-binding protein, 1212-amino acid ABC transporter substrate-binding protein, 2714-methanol/ethanol family PQQ-dependent dehydrogenase, 7610-bifunctional phosphoribosylaminoimidazolecarboxamide formyltransferase/IMP cyclohydrolase, 4015-cytochrome b6-f complex iron-sulfur subunit, 4310-Rieske FeS protein, 2212-ureidoglycolate lyase, 5810-nitrous oxide reductase, and 0604-putative heterocyst to vegetative cell connection protein.</p

2D gel maps for differentially expressed proteins in <i>Anabaena</i> PD-1 cells in the control group.

<p>2D gel maps for differentially expressed proteins in <i>Anabaena</i> PD-1 cells in the control group.</p

Biodegradation of polychlorinated biphenyls (PCBs) by the novel identified cyanobacterium <i>Anabaena</i> PD-1

<div><p>Polychlorinated biphenyls (PCBs), a class of hazardous pollutants, are difficult to dissipate in the natural environment. In this study, a cyanobacterial strain <i>Anabaena</i> PD-1 showed good resistance against PCB congeners. Compared to a control group, chlorophyll <i>a</i> content decreased 3.7% and 11.7% when <i>Anabaena</i> PD-1 was exposed to 2 and 5 mg/L PCBs for 7 d. This cyanobacterial strain was capable of decomposing PCB congeners which was conclusively proved by determination of chloride ion concentrations in chlorine-free medium. After 7 d, the chloride ion concentrations in PCB-treated groups (1, 2, 5 mg/L) were 3.55, 3.05, and 2.25 mg/L, respectively. The genetic information of strain PD-1 was obtained through 16S rRNA sequencing analysis. The GenBank accession number of 16S rRNA of <i>Anabaena</i> PD-1 was KF201693.1. Phylogenetic tree analysis clearly indicated that <i>Anabaena</i> PD-1 belonged to the genus <i>Anabaena</i>. The degradation half-life of Aroclor 1254 by <i>Anabaena</i> PD-1 was 11.36 d; the total degradation rate for Aroclor 1254 was 84.4% after 25 d. Less chlorinated PCB congeners were more likely to be degraded by <i>Anabaena</i> PD-1 in comparison with highly chlorinated congeners. <i>Meta</i>- and <i>para</i>-chlorines in trichlorodiphenyls and tetrachlorobiphenyls were more susceptible to dechlorination than <i>ortho</i>-chlorines during the PCB-degradation process by <i>Anabaena</i> PD-1. Furthermore, <i>Anabaena</i> PD-1 can decompose dioxin-like PCBs. The percent biodegradation of 12 dioxin-like PCBs by strain PD-1 ranged from 37.4% to 68.4% after 25 days. Results above demonstrate that <i>Anabaena</i> PD-1 is a PCB-degrader with great potential for the in situ bioremediation of PCB-contaminated paddy soils.</p></div