Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals

Acclimatory phenotypic response is a common phenomenon in microalgae, particularly during heavy metal stress. It is not clear so far whether acclimating to one abiotic stressor can alleviate the stress imposed by another abiotic factor. The intent of the present study was to demonstrate the implicat...

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Autores principales:	Sudharsanam Abinandan, Kadiyala Venkateswarlu, Mallavarapu Megharaj
Formato:	article
Lenguaje:	EN
Publicado:	Elsevier 2021
Materias:	Abiotic stressors Acclimation Acid-tolerant microalgae Alleviation of metal tolerance Biologically excess concentrations Microalgal strains Microbiology QR1-502 Genetics QH426-470
Acceso en línea:	https://doaj.org/article/abc3933d4d8e478695ebf60a8237a257
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spelling	oai:doaj.org-article:abc3933d4d8e478695ebf60a8237a2572021-11-20T05:14:33ZPhenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals2666-517410.1016/j.crmicr.2021.100081https://doaj.org/article/abc3933d4d8e478695ebf60a8237a2572021-12-01T00:00:00Zhttp://www.sciencedirect.com/science/article/pii/S2666517421000614https://doaj.org/toc/2666-5174Acclimatory phenotypic response is a common phenomenon in microalgae, particularly during heavy metal stress. It is not clear so far whether acclimating to one abiotic stressor can alleviate the stress imposed by another abiotic factor. The intent of the present study was to demonstrate the implication of acidic pH in effecting phenotypic changes that facilitate microalgal tolerance to biologically excess concentrations of heavy metals. Two microalgal strains, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, were exposed to biologically excess concentrations of Cu (0.50 and 1.0 mg L‒1), Fe (5 and 10 mg L‒1), Mn (5 and 10 mg L‒1) and Zn (2, 5 and 10 mg L‒1) supplemented to the culture medium at pH 3.5 and 6.7. Chlorophyll autofluorescence and biochemical fingerprinting using FTIR-spectroscopy were used to assess the microalgal strains for phenotypic changes that mediate tolerance to metals. Both the strains responded to acidic pH by effecting differential changes in biochemicals such as carbohydrates, proteins, and lipids. Both the microalgal strains, when acclimated to low pH of 3.5, exhibited an increase in protein (< 2-fold) and lipid (> 1.5-fold). Strain MAS1 grown at pH 3.5 showed a reduction (1.5-fold) in carbohydrates while strain MAS3 exhibited a 17-fold increase in carbohydrates as compared to their growth at pH 6.7. However, lower levels of biologically excess concentrations of the selected transition metals at pH 6.7 unveiled positive or no effect on physiology and biochemistry in microalgal strains, whereas growth with higher metal concentrations at this pH resulted in decreased chlorophyll content. Although the bioavailability of free-metal ions is higher at pH 3.5, as revealed by Visual MINTEQ model, no adverse effect was observed on chlorophyll content in cells grown at pH 3.5 than at pH 6.7. Furthermore, increasing concentrations of Fe, Mn and Zn significantly upregulated the carbohydrate metabolism, but not protein and lipid synthesis, in both strains at pH 3.5 as compared to their growth at pH 6.7. Overall, the impact of pH 3.5 on growth response suggested that acclimation of microalgal strains to acidic pH alleviates metal toxicity by triggering physiological and biochemical changes in microalgae for their survival.Sudharsanam AbinandanKadiyala VenkateswarluMallavarapu MegharajElsevierarticleAbiotic stressorsAcclimationAcid-tolerant microalgaeAlleviation of metal toleranceBiologically excess concentrationsMicroalgal strainsMicrobiologyQR1-502GeneticsQH426-470ENCurrent Research in Microbial Sciences, Vol 2, Iss , Pp 100081- (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Abiotic stressors Acclimation Acid-tolerant microalgae Alleviation of metal tolerance Biologically excess concentrations Microalgal strains Microbiology QR1-502 Genetics QH426-470
spellingShingle	Abiotic stressors Acclimation Acid-tolerant microalgae Alleviation of metal tolerance Biologically excess concentrations Microalgal strains Microbiology QR1-502 Genetics QH426-470 Sudharsanam Abinandan Kadiyala Venkateswarlu Mallavarapu Megharaj Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals
description	Acclimatory phenotypic response is a common phenomenon in microalgae, particularly during heavy metal stress. It is not clear so far whether acclimating to one abiotic stressor can alleviate the stress imposed by another abiotic factor. The intent of the present study was to demonstrate the implication of acidic pH in effecting phenotypic changes that facilitate microalgal tolerance to biologically excess concentrations of heavy metals. Two microalgal strains, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, were exposed to biologically excess concentrations of Cu (0.50 and 1.0 mg L‒1), Fe (5 and 10 mg L‒1), Mn (5 and 10 mg L‒1) and Zn (2, 5 and 10 mg L‒1) supplemented to the culture medium at pH 3.5 and 6.7. Chlorophyll autofluorescence and biochemical fingerprinting using FTIR-spectroscopy were used to assess the microalgal strains for phenotypic changes that mediate tolerance to metals. Both the strains responded to acidic pH by effecting differential changes in biochemicals such as carbohydrates, proteins, and lipids. Both the microalgal strains, when acclimated to low pH of 3.5, exhibited an increase in protein (< 2-fold) and lipid (> 1.5-fold). Strain MAS1 grown at pH 3.5 showed a reduction (1.5-fold) in carbohydrates while strain MAS3 exhibited a 17-fold increase in carbohydrates as compared to their growth at pH 6.7. However, lower levels of biologically excess concentrations of the selected transition metals at pH 6.7 unveiled positive or no effect on physiology and biochemistry in microalgal strains, whereas growth with higher metal concentrations at this pH resulted in decreased chlorophyll content. Although the bioavailability of free-metal ions is higher at pH 3.5, as revealed by Visual MINTEQ model, no adverse effect was observed on chlorophyll content in cells grown at pH 3.5 than at pH 6.7. Furthermore, increasing concentrations of Fe, Mn and Zn significantly upregulated the carbohydrate metabolism, but not protein and lipid synthesis, in both strains at pH 3.5 as compared to their growth at pH 6.7. Overall, the impact of pH 3.5 on growth response suggested that acclimation of microalgal strains to acidic pH alleviates metal toxicity by triggering physiological and biochemical changes in microalgae for their survival.
format	article
author	Sudharsanam Abinandan Kadiyala Venkateswarlu Mallavarapu Megharaj
author_facet	Sudharsanam Abinandan Kadiyala Venkateswarlu Mallavarapu Megharaj
author_sort	Sudharsanam Abinandan
title	Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals
title_short	Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals
title_full	Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals
title_fullStr	Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals
title_full_unstemmed	Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals
title_sort	phenotypic changes in microalgae at acidic ph mediate their tolerance to higher concentrations of transition metals
publisher	Elsevier
publishDate	2021
url	https://doaj.org/article/abc3933d4d8e478695ebf60a8237a257
work_keys_str_mv	AT sudharsanamabinandan phenotypicchangesinmicroalgaeatacidicphmediatetheirtolerancetohigherconcentrationsoftransitionmetals AT kadiyalavenkateswarlu phenotypicchangesinmicroalgaeatacidicphmediatetheirtolerancetohigherconcentrationsoftransitionmetals AT mallavarapumegharaj phenotypicchangesinmicroalgaeatacidicphmediatetheirtolerancetohigherconcentrationsoftransitionmetals
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Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals

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