Presence or Absence of mlr Genes and Nutrient Concentrations Co-Determine the Microcystin Biodegradation Efficiency of a Natural Bacterial Community.
The microcystin biodegradation potential of a natural bacterial community coexisting with a toxic cyanobacterial bloom was investigated in a water reservoir from central Spain. The biodegradation capacity was confirmed in all samples during the bloom and an increase ofmlrA gene copies was found with increasing microcystin concentrations. Among the 24 microcystin degrading strains isolated from the bacterial community, only 28% showed presence ofmlrA gene, strongly supporting the existence and abundance of alternative microcystin degradation pathways in nature. In vitro degradation assays with bothmlr⁺ andmlr-bacterial genotypes (with presence and absence of the completemlrgene cluster, respectively) were performed with four isolated strains (Sphingopyxissp. IM-1, IM-2 and IM-3;Paucibacter toxinivoransIM-4) and two bacterial degraders from the culture collection (Sphingosinicella microcystinivoransY2;Paucibacter toxinivorans2C20). Differences in microcystin degradation efficiencies between genotypes were found under different total organic carbon and total nitrogen concentrations. Whilemlr⁺ strains significantly improved microcystin degradation rates when exposed to other carbon and nitrogen sources,mlr-strains showed lower degradation efficiencies. This suggests that the presence of alternative carbon and nitrogen sources possibly competes with microcystins and impairs putative non-mlrmicrocystin degradation pathways. Considering the abundance of themlr-bacterial population and the increasing frequency of eutrophic conditions in aquatic systems, further research on the diversity of this population and the characterization and conditions affecting non-mlrdegradation pathways deserves special attention.
IMDEA Water Institute, Alcalá de Henares, Madrid 28805, Spain. angeles.lezcano@imdea.org.
María Ángeles
MÁ
Lezcano
IMDEA Water Institute, Alcalá de Henares, Madrid 28805, Spain. jesus.moron@imdea.org.
Jesús
J
Morón-López
Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin 12587, Germany. agha@igb-berlin.de.
Ramsy
R
Agha
IMDEA Water Institute, Alcalá de Henares, Madrid 28805, Spain. isabel.lopez@imdea.org.
Isabel
I
López-Heras
IMDEA Water Institute, Alcalá de Henares, Madrid 28805, Spain. leonor.nozal@imdea.org.
Leonor
L
Nozal
Departamento de Biología, Universidad Autónoma de Madrid, Cantoblanco 28049, Spain. antonio.quesada@uam.es.
Antonio
A
Quesada
IMDEA Water Institute, Alcalá de Henares, Madrid 28805, Spain. rehab@imdea.org.
Rehab
R
El-Shehawy
D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D002244:Carbon / Q000032:analysis; D005068:Eutrophication; D005798:Genes, Bacterial; D005838:Genotype; D052998:Microcystins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis; D012336:RNA, Ribosomal, 16S; D014871:Water Microbiology; D014873:Water Pollutants / Q000032:analysis / Q000378:metabolism*
D052998:Microcystins; D012336:RNA, Ribosomal, 16S; D014873:Water Pollutants; D002244:Carbon; D009584:Nitrogen
Paucibacter sp.; Sphingopyxis sp.; biodegradation; cyanobacteria; genotype; microcystin