Figure 1.
MC-LR structure and potential degradation pathways in bacteria.
Steps of the known cleavage pathway are linked by solid arrows. Steps through xenobiotic metabolism are linked by dotted arrows. Overrepresented genes in the MC metagenomes are labeled with asterisks and bold fonts. Unknown genes are labeled with question marks. Triangle indicates the cleavage site of mlrA. Ala: alanine, Arg: arginine, Adda: 3-amino-9-methoxy-2, 6, 8-trimethyl-10-phenyldeca-4, 6-dienoic acid, Cys: cysteine, Glu: glutamic acid, GSH: glutathione, Leu: leucine, MeAsp: methylaspartic acid.
Figure 2.
Variation of MC-LR concentration and total bacterial cell number during microcosm incubation.
(A) Average MC-LR concentrations and standard deviations in the MC and FW-MC microcosms. (B) Average bacterial abundance and standard deviations in MC and CT microcosms. Shaded areas indicate periods of pre-incubation with inorganic N and P for establishing carbon-limited conditions in microcosms.
Figure 3.
Distribution of bacterial cells of high (HI) and low (LI) metabolic activities during microcosm incubation.
(A) Flow cytometric analysis of bacterial cell distribution in the MC and CT microcosms after 48 hours of incubation. (B) Average relative abundance of HI and LI cells in the MC and CT microcosms during the course of incubation. (C) Average numbers of HI and LI cells and standard deviations in the MC and CT microcosms during the course of incubation.
Figure 4.
Clustering pattern of bacterioplankton 16S rRNA gene contents based on T-RFLP analysis.
Cluster analysis of T-RFLP data for original water samples (Ori 1 and 2), samples at the end of inorganic nutrient pre-incubation (Pre-incub 1 and 2) and samples at the end of MC-LR incubation experiments in the microcystin amended (MC1–48 h and MC2–48 h) and control (CT1–48 h and CT2–48 h) microcosms.
Table 1.
Sequence annotation statistics for the MC and CT metagenomes.
Figure 5.
Significantly overrepresented gene categories in the MC metagenomes, relative to those in the CT metagenomes.
(A) General COG categories. (B) General KEGG categories. Calculations were based on relative abundance of each gene categories between the MC and CT metagenomes. Significance overrepresentation was reported when OR>1, P<0.02.
Table 2.
Overrepresented COG groups in the MC metagenomes relative to the CT metagenomes, based on odds ratios (OR) calculated between the copy number of putative gene sequences in the MC and CT metagenomes.
Table 3.
Significantly enriched KEGG pathways in the MC metagenomes relative to the CT metagenomes, based on odds ratios (OR) calculated between the copy number of putative gene sequences in the MC and CT metagenomes.
Figure 6.
Taxonomic distribution of COG sequences in the MC and CT metagenomes.
(A) At the order level. (B) At the family level. (C) At the genus level. Only major taxa are shown (collectively accounted for >4% of total metagenomic sequences). Asterisks are to label bacterial taxa with different relative abundance between the MC and CT metagenomes (OR >1, P<0.02).
Figure 7.
Percent distribution of major bacterial orders that were affiliated with GST and mlr genes.