title: Induction of temperate cyanophage AS-1 by heavy metal--copper.
abstract: BACKGROUND
  It has been reported that some marine cyanophage are temperate and can be induced from a lysogenic phase to a lytic phase by different agents such as heavy metals. However, to date no significant reports have focused on the temperate nature of freshwater cyanophage/cyanobacteria. Previous experiments with cyanophage AS-1 and cyanobacteria Anacystis nidulans have provided some evidence that AS-1 may have a lysogenic life cycle in addition to the characterized lytic cycle.
  
  
  RESULTS
  In this study, the possible temperate A. nidulans was treated with different concentrations of heavy metal-copper. CuSO4 with concentrations of 3.1 x 10(-3) M, 3.1 x 10(-4) M, 3.1 x 10(-5) M and 3.1 x 10(-6) M were used to detect the induction of AS-1 from A. nidulans. The population of the host, unicellular cyanobacteria Anacystis nidulans, was monitored by direct count and turbidity while the amount of virus produced was derived from plaque forming units (PFU) by a direct plating method. The ratio of AS-1 release from A. nidulans was also determined. From these results it appears that AS-1 lysogenic phage can be induced by copper at concentrations from 3.1 x 10(-6) M to 3.1 x 10(-4) M. Maximal phage induction occurred at 6 hours after addition of copper, with an optimal concentration of 3.1 x 10(-6) M.
  
  
  CONCLUSIONS
  Cu2+ is a significant inducer for lysogenic cyanobacterial cells and consequently would be a potential control agent in the cyanobacteria population in fresh water ecosystems.
authors.affiliation: Department of Biology & Molecular Biology, Montclair State University, Montclair, NJ 07043, USA. leel@mail.montclair.edu
authors.forename: Lee H
authors.initials: LH
authors.lastname: Lee
authors.forename: Doris
authors.initials: D
authors.lastname: Lui
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Platner
authors.forename: Shi-Fang
authors.initials: SF
authors.lastname: Hsu
authors.forename: Tin-Chun
authors.initials: TC
authors.lastname: Chu
authors.forename: John J
authors.initials: JJ
authors.lastname: Gaynor
authors.forename: Quinn C
authors.initials: QC
authors.lastname: Vega
authors.forename: Bonnie K
authors.initials: BK
authors.lastname: Lustigman
mesh_terms: D001435:Bacteriophages / Q000187:drug effects* / Q000502:physiology; D019327:Copper Sulfate / Q000494:pharmacology*; D000458:Cyanobacteria / Q000187:drug effects / Q000821:virology*; D017753:Ecosystem; D005618:Fresh Water / Q000382:microbiology / Q000821:virology; D010948:Viral Plaque Assay; D014775:Virus Activation / Q000187:drug effects*
chemical_list: D019327:Copper Sulfate