Microcystis Aeruginosa Needs a Microbiome in Order to Utilize Phosphorus from Organo-Phosphates

Abstract

Microcystis aeruginosa is a toxin producing cyanobacterium responsible for dangerous Harmful Algal Blooms (HABs) in Lake Okeechobee Florida as well as worldwide. We investigated the potential utilization of organophosphates, as Dissolved Organophosphates (DOP), by this species to expand the knowledge of and eventually controls on nutrient sources and pollution. Axenic M. aeruginosa (PCC7806), which grew well on standard BG-11 media containing potassium dibasic hydrogen phosphate (K2PO4), was found to be unable to utilize certain organo-phosphates (D-Glucose-6-Phosphate {DG6P}, B-Glycerol-Phosphate {BGP}, Phytic Acid {PhA}). Non-axenic M. aeruginosa (UTEX LB2385) grew well on both standard BG-11 and BG-11 media in which the normal inorganic phosphate was substituted with DG6P or BGP but not with PhA. Heterotrophic bacteria in the non-axenic culture likely cleaved ortho-phosphate from the organophosphates while utilizing the organic portion as ‘food’. The addition of alkaline bovine phosphatase to the axenic cultures did not facilitate utilization of organophosphates. Letting the axenic cultures enter the lysis (death) phase did not allow activation of intrinsic phosphatase enzymes as added orgo-phosphates did not reactivate growth. Co-culturing M. aeruginosa with Anabaena flos-aquae, known to utilize phosphatase enzymes, did not provide phosphorus for M. aeruginosa. Collectively, these results reconfirm the concept of a synergistic microbiome (phycosphere, ‘interactome’) being required for the utilization of organophosphates as a phosphorus source by Microcystis aeruginosa.