Morphological changes in an acidophilic bacterium induced by heavy metals

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Acidiphilium strains are adapted to acidic mine environments with various stresses.
• Morphological changes are a bacterial stress response, but unstudied in Acidiphilium.
• This study investigates Acidiphilium symbioticum H8's response to heavy metals.

Purpose of the Study:

• To investigate the morphological changes in Acidiphilium symbioticum H8 under heavy metal stress.
• To determine the effect of specific heavy metals (Cu, Cd, Ni, Zn) on cell morphology.
• To elucidate the mechanism of metal-induced morphological alterations.

Main Methods:

• Exposure of Acidiphilium symbioticum H8 to sub-inhibitory and inhibitory concentrations of Cu, Cd, Ni, and Zn.
• Microscopic observation of cell morphology (shape, aggregation, chain formation).
• Scanning electron microscopy with energy dispersive X-ray analysis for metal deposition.
• Inductively coupled plasma mass spectrometry to measure ion substitution.

Main Results:

• Sub-inhibitory concentrations of Cu and Cd caused maximum size alterations.
• Cd induced lenticular-shaped cell chains; Cu induced round cells; Ni caused aggregation; Zn had no effect.
• Metal deposition on cell surfaces was confirmed, with replacement of cell-bound Ca2+ ions.
• Morphological changes occurred specifically at sub-inhibitory metal concentrations.

Conclusions:

• Acidiphilium symbioticum H8 exhibits distinct morphological responses to different heavy metals.
• Heavy metal-induced shape changes involve the displacement of Ca2+ ions.
• Morphological plasticity is a key survival strategy for Acidiphilium in metal-polluted environments.