Amino acid transport in taxonomically diverse cyanobacteria and identification of two genes encoding elements of a neutral amino acid permease putatively involved in recapture of leaked hydrophobic amino acids

Abstract

The activities of uptake of thirteen 14 C-labeled amino acids were determined in nine cyanobacteria, including the unicellular strains Synechococcus sp. strain PCC 7942 and Synechocystis sp. strain PCC 6803; the filamentous strain Pseudanabaena sp. strain PCC 6903, and the filamentous, heterocyst-forming strains Anabaena sp. strains PCC 7120 and PCC 7937; Nostoc sp. strains PCC 7413 and PCC 7107; Calothrix sp. strain PCC 7601 (which is a mutant unable to develop heterocysts); and Fischerella muscicola UTEX 1829. Amino acid transport mutants, selected as mutants resistant to some amino acid analogs, were isolated from the Anabaena, Nostoc, Calothrix, and Pseudanabaena strains. All of the tested cyanobacteria bear at least a neutral amino acid transport system, and some strains also bear transport systems specific for basic or acidic amino acids. Two genes, natA and natB, encoding elements (conserved component, NatA, and periplasmic binding protein, NatB) of an ABC-type permease for neutral amino acids were identified by insertional mutagenesis of strain PCC 6803 open reading frames from the recently published genomic DNA sequence of this cyanobacterium. DNA sequences homologous to natA and natB from strain PCC 6803 were detected by hybridization in eight cyanobacterial strains tested. Mutants unable to transport neutral amino acids, including natA and natB insertional mutants, accumulated in the extracellular medium a set of amino acids that always included Ala, Val, Phe, Ile, and Leu. A general role for a cyanobacterial neutral amino acid permease in recapture of hydrophobic amino acids leaked from the cells is suggested.

Functional distinctness in the exoproteomes of marine Synechococcus

“…as additional nitrogen sources) as part of a mixotrophic lifestyle. Indeed, picocyanobacteria are known for their ability to acquire amino acids and carbohydrates (Montesinos et al ., 1997; Zubkov et al ., 2003; Mary et al ., 2008; Muñoz‐Marín et al ., 2013) at low nanomolar concentrations, potential products of chitinase or protease activity. It is also possible that these exoenzymes may have a role in eliminating competitors, especially diatoms, because the latter contain chitin in their silica cell wall (Brunner et al ., 2009).…”

The sRNA NsiR4 is involved in nitrogen assimilation control in cyanobacteria by targeting glutamine synthetase inactivating factor IF7

“…To induce nitrogen deficiency, cells were spin down by centrifugation and resuspended in NO − 3 -free BG11. Anabaena 7120 WT and the ntcA mutant strain CSE2 (51) were grown in CO 2 -enriched air, 1% (vol/vol), in BG11 without NO − 3 and supplemented with 6 mM NH 4 Cl, 12 mM TES-NaOH (pH 7.5), and 10 mM NaHCO 3 . The generation of NsiR4 mutants and further growth conditions are described in SI Appendix in detail.…”

“…Cyanobacteria use different inorganic and organic sources of combined nitrogen, such as ammonium (NH + 4 ), nitrate (NO − 3 ), nitrite (NO − 2 ) and urea, or some amino acids (3)(4)(5)(6). Intracellularly, NO − 3 , NO − 2 , and urea are converted to NH + 4 .…”

“…The cells were grown in 250-mL Erlenmeyer flasks containing 100 mL BG11 and 17.6 mM NO − 3 . After reaching an OD 750 of ∼0.8, 2 μM CuSO 4 was added, and after further incubation for 24 h, 10 mM NH 4 Cl was added to the cultures (indicated with an arrow). Amino acids were extracted from cells before and after NH + 4 addition and quantified through HPLC.…”

“…For analysis of inactivating factor (IF) accumulation, 2 μM CuSO 4 was added to induce the petE promoter 8 h before addition of 10 mM NH 4 Cl and 20 mM TES-NaOH (pH 7.5). Extracts were prepared using glass beads as previously described (56).…”