Phosphite cannot be used as a phosphorus source but is non-toxic for microalgae

Abstract

Phosphorous (P) plays a critical role for all living organisms as a structural component of RNA, DNA and phospholipids. Microalgae are autotrophs organisms that have been reported to only assimilate the fully oxidized phosphate (Pi) as P source. However, there are microorganisms capable of utilizing P reduced compounds (i.e. phosphite (Phi) and hypophosphite) as a sole P source, such as bacteria and cyanobacteria. In this study, we evaluated whether microalgae, such as Chlamydomonas reinhardtii, Botryococcus braunii and Ettlia oleoabundans, are capable of using Phi as a sole P source. Our studies revealed that these three microalgae are unable to use Phi as a sole P source. We also found that when Phi is present at concentrations equal or higher than that of Pi, Phi has an inhibitory effect on C. reinhardtii growth. However, since C. reinhardtii was able to survive for a long period of cultivation in the presence of high concentrations of Phi and to recover cell division capacity after transfer to media containing Pi, we noticed that Phi is not toxic for this microalga. We propose that the inhibitory effect of Phi on C. reinhardtii growth might be caused, at least in part, by a competition between the transport of Pi and Phi.

A Review of the Latest in Phosphorus Fertilizer Technology: Possibilities and Pragmatism

“…Because Phi is not metabolized by algae, algal bloom issues might be lessened in freshwater systems receiving P from farm runoff or tile drain leaching. The compound does not appear to be lethal to algae but inhibits growth through competition with OP much like the observations reported on terrestrial experiments (Loera‐Quezada et al, 2015). The rate of microbial oxidation from Phi to OP will likely dictate the efficacy with respect to this facet of the proposed system.…”

A novel genetic engineering platform for the effective management of biological contaminants for the production of microalgae

“…Previously, we reported that some microalgae (i.e. ; Botryococcus braunii and Ettlia oleoabundans ) were unable to metabolize Phi as a P source (Loera‐Quezada et al ., ). As part of this work, we determined that other microalgae including Haematococcus pluvialis and S. obliquus were also unable to metabolize Phi (Figure S3).…”

“…For this purpose, we tested the growth of cells harvested from media containing 1 mM Pi (P-replete cells) or from media devoid of a P source (P-starved cells) in medium supplemented with 0.1 mM Phi as P source in a Multicultivator photobioreactor (MC 1000, Qubit Systems; Qubit Biology Inc. Kingston, Ontario, Canada) ( Figure 1a). We tested Preplete and P-starved cells because we have previously observed that cells grown in 1 mM Pi are able to sustain significant growth in media lacking a P source (Loera-Quezada et al, 2015). We observed that after 6 days of cultivation in media containing Phi as a sole P source the putative ptxD transgenic lines were all capable of growing with a growth rate similar to that of the WT or the same transgenic lines in media containing Pi as a P source ( Figure 1; compare panel b versus c).…”

“…In contrast to prokaryotes, no evidence exists suggesting that eukaryotic organisms have the required genes for the metabolism of any P reduced compound. In fact, it has been extensively documented that plants cannot metabolize Phi (Ávila et al ., ; Berkowitz et al ., ) and more recently, we showed that a number of microalgae species, including Chlamydomonas reinhardtii , Ettlia oleoabundans and Botryococcus braunii, are unable to use Phi as a sole P source (Loera‐Quezada et al ., ). To develop microalga that can be used to design systems to prevent undesirable contaminations in open or closed cultivation systems, we designed a system to make cells able to metabolize Phi, a nonmetabolizable compound, as a sole P source.…”

Análisis Ecotoxicológico Del Fungicida Fosfito De Sodio Sobre Una Comunidad Planctónica

“…La ausencia de efectos tóxicos de los fosfitos sobre el fitoplancton ya había sido demostrada con anterioridad. Concentraciones entre 7.9 y 158.17 mg/L de fosfito potásico monobásico no presentaron efectos tóxicos que causaran mortalidad de las células para la microalga Chlamydomonas reinhardtii (Loera-Quezada et al 2015). En el caso de la cianobacteria Microcystis aeruginosa, se ha observado que el fosfito parece ser inerte y no tóxico hasta concentraciones de 500 mg/L (Zhang et al 2011).…”