Characterization of manganese superoxide dismutase from a marine cyanobacterium Leptolyngbya valderianaBDU20041

Abstract

BackgroundCyanobacteria are recognized as the primordial organisms to grace the earth with molecular oxygen ~3.5 billion years ago as a result of their oxygenic photosynthesis. This laid a selection pressure for the evolution of antioxidative defense mechanisms to alleviate the toxic effect of active oxygen species (AOS) in cyanobacteria. Superoxide dismutases (SODs) are metalloenzymes that are the first arsenal in defense mechanism against oxidative stress followed by an array of antioxidative system. Unlike other living organisms, cyanobacteria possess multiple isoforms of SOD. Hence, an attempt was made to demonstrate the oxidative stress tolerance ability of marine cyanobacterium, Leptolyngbya valderiana BDU 20041 and to PCR amplify and sequence the SOD gene, the central enzyme for alleviating stress.ResultL. valderiana BDU 20041, a filamentous, non-heterocystous marine cyanobacterium showed tolerance to the tested dye (C.I. Acid Black 1) which is evident by increased in biomass (i.e.) chlorophyll a. The other noticeable change was the total ROS production by culture dosed with dye compared to the control cultures. This prolonged incubation showed sustenance, implying that cyanobacteria maintain their antioxidant levels. The third significant feature was a two-fold increase in SOD activity of dye treated L. valderiana BDU20041 suggesting the role of SOD in alleviating oxidative stress via Asada-Halliwell pathway. Hence, the organism was PCR amplified for SOD gene resulting in an amplicon of 550 bp. The sequence analysis illustrated the presence of first three residues involved in motif; active site residues at H4, 58 and D141 along with highly conserved Mn specific residues. The isolated gene shared 63.8% homology with MnSOD of bacteria confirmed it as Mn isoform. This is the hitherto report on SOD gene from marine cyanobacterium, L. valderiana BDU20041 of Indian subcontinent.ConclusionGeneration of Reactive Oxygen Species (ROS) coupled with induction of SOD by marine cyanobacterium, L. valderiana BDU20041 was responsible for alleviating stress caused by an azo dye, C. I. Acid Black 1. The partial SOD gene has been sequenced and based on the active site, motif and metal specific residues; it has been identified as Mn metalloform.

Ultraviolet radiation and cyanobacteria

“…The primitive unicellular Prochlorococcus expresses only NiSOD, whereas the developed middle-order forms of cyanobacteria express a combination of Fe-NiSOD and Fe-MnSOD [75]. Priya et al recently characterized the MnSOD from the marine cyanobacterium Leptolyngbya valderiana BDU20041 [76]. In another cyanobacterium, Anabaena PCC 7120, MnSOD is involved in the acclimation of the strain to high light levels and MnSOD is required for the protection of nitrogenase from ROS [77].…”

Overexpression of Cu/Zn Superoxide Dismutase (Cu/Zn SOD) in Synechococcus elongatus PCC 7942 for Enhanced Azo Dye Removal through Hydrogen Peroxide Accumulation

“…The expression of this Cu/Zn SOD was slightly increased after 24 h of growth in dye-containing medium ( Figure 3 B). A similar report [ 37 ] documented the increased expression of SOD by twofold in cyanobacterium Leptolyngbya valderiana BDU 20,041 when grown in medium containing acid black dye to alleviate the oxidative stress and for sustenance in growth. However, to make a very efficient H 2 O 2 producing system, it might be necessary to enhance the expression of target SODs as that of heterologous expression of human Cu/Zn SOD in Anacystis nidulans 6301 under the control of strong light-driven Ribulose-1,5-bisphosphate Carboxylase/oxygenase ( rbc ) promoter [ 10 ].…”

Cyanobacteria as the Source of Antioxidants

“…All have metal redox-active centers that, respectively, include Fe (III), Cu (II), Zn (II), Mn (III), and Ni (II/III) at the active site [44]. Cyanobacteria have all four kinds of SOD, and many cyanobacterial species include more than one type of SOD [45]. It should be emphasized that some actinobacteria and archaea have a single gene that, depending on the environment, can either make FeSOD or MnSOD [46].…”