Novel cyanobacterial bioreporters of phosphorus bioavailability based on alkaline phosphatase and phosphate transporter genes of Anabaena sp. PCC 7120

Abstract

There is heterogeneity in the way cyanobacteria respond to P starvation and subsequently how they adapt to environments with low or fluctuating P concentrations. In this study, we have fused the promoterless lux operon luxCDABE to the promoter regions of Anabaena sp. PCC 7120 phoA genes putatively encoding alkaline phosphatases, phoA (all2843) and phoA-like (alr5291) and to the promoter region of one operon putatively encoding a high affinity phosphate transporter pst1 (all4575-4572). The self-bioluminescent strains constructed in this way, Anabaena AP (phoA promoter), Anabaena AP-L (phoA-like promoter), and Anabaena PST (pst1 promoter) have been used to study the expression of these genes in response to P starvation and P re-feeding with inorganic and organic phosphate sources. Our data showed that the pst1 promoter was activated at much higher level than the phoA-like promoter following P starvation; however, we did not observe activation of the phoA promoter. The P re-feeding experiments revealed that both strains, Anabaena (A.) PST and A. AP-L could be used as novel bioreporters of P availability in environmental samples. Both strains were used to estimate bioavailable P in environmental samples (fresh- and wastewaters) with a wide range of soluble P concentrations. The results indicated that most of the P in the water samples was in chemical forms available to the cyanobacterium; however there were some differences in the estimates given by both strains as A. PST appeared to be more adequate for the samples with the lowest P load while A. AP-L gave similar or even higher values of P concentrations than those chemically measured in samples with higher P load.

Characterization of a Chromosomal Type II Toxin–Antitoxin System mazEaFa in the Cyanobacterium Anabaena sp. PCC 7120

“…A long-term (at least 6 days) deprivation of phosphorus source also caused a reversible growth cessation of Anabaena sp. PCC 7120 [34]. Our data presented here show that the effect of mazEaFa -encoded products on growth of Anabaena or E. coli resembles the stress-induced reversible growth arrest.…”

“…High-light exposure could reduce the photosynthetic electron transport components of cyanobacteria, resulting in excess production of reactive oxygen species (ROS) and eventually oxidative stress [35]. The nutrient limitation would inhibit growth of cyanobacteria [34], [36]. We thus examined whether the mazEaFa deletion could affect the growth of Anabaena under these major environmental stresses [35].…”

“…High-light exposure or phosphate limitation experiments were performed according to previous methods [33], [34] but simply modified here. To analyze the effects of high-light intensities, Anabaena cultures with an initial OD 730 of 0.2 were grown under the light of 30, 100, 200 or 300 µmol photons/m 2 s 1 .…”

Response of Alkaline Phosphatases in the Cyanobacterium Anabaena sp. FACHB 709 to Inorganic Phosphate Starvation

“…PCC 7120 APases indicates that only PhoS (Alr5291) was expressed under P-replete conditions, and is significantly induced after P i starvation. Conversely, PhoA (All2843) was neither expressed in P-replete medium nor respond to P starvation even after prolonged P i starvation [10]. However, in FACHB 709, the APase homologs of Anabaena sp.…”

“…Of these genes, only the product of all2843 has been identified as a phosphomonoesterase by complementation test using the PhoA-deficient Escherichia coli strain [9]. A transcriptional analysis showed that P i starvation induced the expression of alr5291 but not all2843 [10].…”