Physiological and biochemical alterations in <i>Anabaena </i>7120 under iron stress

Abstract

Various physiological and biochemical process like growth, NO₃^--uptake, nitrate reductase, glutamine synthetase and ATPases (Mg²⁺and Ca²⁺ dependent) in the cyanobacterium <i>Anabaena </i>7120 were observed under iron stress. Growth was found to be maximum in 50 <i>μM</i> Fe³⁺ added cells however, 20 <i>μM </i>Fe³⁺ (the Fe³⁺ concentration generally used for routine culturing of cyanobacterial cell in Chu 10 medium) incubation resulted in lower growth. Fe³⁺ starvation on the other hand showed very poor growth up to 4^th day but once the growth started it reached at significant level on 7^th day. Higher Fe³⁺concentration reflected reduced growth with lethality at 500 <i>μM </i>Fe³⁺. Chlorophyll <i>a </i>fluorescence under Fe³⁺ stress reflected almost the similar results as in case of growth. However, the pigment was found to be more sensitive as compared to protein under Fe³⁺ stress. Similar results have been observed in case of NO₃ uptake with only 80% reduction in nutrient uptake in <i>500 μM </i>Fe³⁺ incubated cells. Nitrate reductase activity was lower in Fe³⁺ starved cells as compared to significant enzyme

activity in 20 and 50 <i>μM </i>Fe³⁺ incubated cells. Similar to nitrate reductase, glutamine synthetase also showed maximum level in 50 <i>μM </i>Fe³⁺ added cells, however, higher Fe³⁺ concentration (300-500 <i>μM </i>) resulted in reduced enzymatic activity. Glutamine synthetase activity was less sensitivity as compared to nitrate reductase activity under Fe³⁺ stress. ATPase (Mg²⁺

<span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">and Ca²⁺ dependent) always showed higher level with increasing Fe³⁺ concentration.</span>