Abstract:
Microalgae
interact with mineral particles in aqueous environment, yet how clay
minerals affect physiological processes in algal cells remain
unexplored. In this study, we compared the effects of palygorskite (Pal)
and montmorillonite (Mt), which respectively represent fibrous and
layered clay minerals, on the physiological processes ofChlamydomonas reinhardtii . It was observed that C.
reinhardtii responded differently to the treatments of Pal and Mt. The
Pal particles bound tightly to and even inserted cells, resulting in a
significantly decrease of cell numbers from 27.35 to
21.02*107 mL-1. However, Mt was only
loosely attached to the cell surface. The photosynthesis in the algal
cells was greatly inhibited by Pal, with rETRmaxsignificantly reduced from 103.80 to 56.67 μmol electrons
m-2s-1. Several key genes involved
in photosynthesis, namely IF2CP, psbH and OHP1,
were also downregulated. In
addition, Pal reduced the quantities of proteins and polysaccharides in
extracellular polymeric substances (EPS) and the P uptake by C.
reinhardtii when the P level in the culture was 3.15 mg/L. However, no
significant changes were found regarding the above EPS components or the
amount of P in algal cells upon the addition of Mt. Together, the
impacts of fibrous Pal on C. reinhardtii was more profound than
those of layered Mt.