Role of calcium in acclimation of the cyanobacterium Synechococcus elongatus PCC 7942 to nitrogen starvation

Abstract

A Ca2+ signal is required for the process of heterocyst differentiation in the filamentous diazotrophic cyanobacterium Anabaena sp. PCC 7120. This paper presents evidence that a transient increase in intracellular free Ca2+ is also involved in acclimation to nitrogen starvation in the unicellular non-diazotrophic cyanobacterium Synechococcus elongatus PCC 7942. The Ca2+ transient was triggered in response to nitrogen step-down or the addition of 2-oxoglutarate (2-OG), or its analogues 2,2-difluoropentanedioic acid (DFPA) and 2-methylenepentanedioic acid (2-MPA), to cells growing with combined nitrogen, suggesting that an increase in intracellular 2-OG levels precedes the Ca2+ transient. The signalling protein PII and the transcriptional regulator NtcA appear to be needed to trigger the signal. Suppression of the Ca2+ transient by the intracellular Ca2+ chelator N,N′-[1,2-ethanediylbis(oxy-2,1-phenylene)]bis[N-[2-[(acetyloxy)methoxy]-2-oxoethyl]]-,bis[(acetyloxy)methyl] ester (BAPTA-AM) inhibited expression of the glnB and glnN genes, which are involved in acclimation to nitrogen starvation and transcriptionally activated by NtcA. BAPTA-AM treatment partially inhibited expression of the nblA gene, which is involved in phycobiliprotein degradation following nutrient starvation and is regulated by NtcA and NblR; in close agreement, BAPTA-AM treatment partially inhibited bleaching following nitrogen starvation. Taken together, the results presented here strongly suggest an involvement of a defined Ca2+ transient in acclimation of S. elongatus to nitrogen starvation through NtcA-dependent regulation.

Extreme cellular adaptations and cell differentiation required by a cyanobacterium for carbonate excavation

“…Intracellular Calcium Dynamics. Cyanobacteria show a very tight regulation of Ca 2+ i levels, typically in the low nanomolar range (15,20,21), but Ca 2+ pumping in euendoliths could potentially create transient or even continued intracellular hyperaccumulation (10). We used several approaches to probe Ca 2+ i in strain BC008.…”

Proteome Analysis of B. subtilis in Response to Calcium

“…In addition, a 2DE proteomic analysis showed that the synthesis of EF-Tu is affected by Ca 2+ levels [43]. ] i levels have been more frequently studied in E. coli and cyanobacteria [13][14][15]19], limited studies have been done in B. subtilis. Our results indicate that indeed B. subtilis tightly controls cytosolic calcium and we concur with other studies [16] in that intracellular calcium levels regulate the expression of many genes and the synthesis of proteins.…”

“…Indirect evidence suggests that Ca 2+ may play a role in various bacterial physiological processes such as spore formation, chemotaxis, heterocyst differentiation, transport and virulence [9][10][11][12]. Several reports have shown that bacteria are capable of maintaining intracellular Ca 2+ homeostasis, and Ca 2+ transients are produced in response to adaptation to nitrogen starvation, environmental stress [13][14][15][16], and metabolites of carbohydrate metabolism [17,18]. These findings suggest a regulatory role for Ca 2+ in bacteria.…”

A Pseudomonas aeruginosa EF-Hand Protein, EfhP (PA4107), Modulates Stress Responses and Virulence at High Calcium Concentration

“…Ca 2+ is a part of a hyperinflamatory host response to bacterial infection, and accumulates in airway epithelia, pulmonary and nasal liquids of CF patients [10], [11]. There is growing evidence suggesting that Ca 2+ also plays a significant role in the physiology of certain bacteria, affecting maintenance of cell structure, motility, chemotaxis, cell division and differentiation, gene expression, transport, and spore formation [12], [13], [14], [15], [16]. Several bacteria including P. aeruginosa have been shown to maintain intracellular Ca 2+ at sub-micromolar levels and produce Ca 2+ transients in response to environmental and physiological factors [17]–[19].…”