Possible involvement of a 72-kDa polypeptide in nucleotide excision repair of Chlorella pyrenoidosa identified by affinity adsorption and repair synthesis assay

Effects of chloramphenicol, florfenicol, and thiamphenicol on growth of algae Chlorella pyrenoidosa, Isochrysis galbana, and Tetraselmis chui

This study investigated the growth inhibition effects of three phenicol antibiotics on microalgae used in aquaculture. Different dose levels of chloramphenicol (CAP), florfenicol (FF), and thiamphenicol (TAP) were added to cultures of one freshwater green alga, Chlorella pyrenoidosa, and two marine algae, Isochrysis galbana and Tetraselmis chui. For the two marine algae, FF showed higher toxicity levels (EC50, 1.3-8 mg l(-1)) than CAP (4-41 mg l(-1)) and TAP (38-158 mg l(-1)). CAP was more toxic to the freshwater algae (EC50, 14 mg l(-1)) than FF (215 mg l(-1)) and TAP (1283 mg l(-1)). TAP was the least toxic to the three algae, but maintained the highest stability during the test period. Among the tested algae, T. chui was the species most sensitive to the three antibiotics. This study demonstrates that all three phenicol antibiotics can inhibit growth of the three microalgae and should be carefully used in aquaculture.

DNA mismatch binding activities in Chlorella pyrenoidosa extracts and affinity isolation of G-T mismatch binding proteins

DNA mismatch recognition proteins contained in the extracts of unicellular alga Chlorella pyrenoidosa were isolated by affinity adsorption and 2-D gel electrophoresis. Incubation of the algal extracts with a 38-mer duplex oligonucleotide carrying a single DNA simple mispair generated a few gel retardation complexes. G-T mispair was recognized significantly better than C-T, G-G, G-A, and C-C mispairs by the algal extracts and these extracts bound very weakly to G-A and C-C mispairs, displaying a universal trend of mismatch binding efficiency. The levels of mismatch recognition complexes were slightly increased in the presence of 1 mM ATP. Two 13-kDa G-T binding polypeptides possessing pIs of 5.3 and 5.5 were isolated after resolving affinity-captured proteins by 2-D gel electrophoresis and the two factors were found to bind 5.5- and 2.8-fold stronger to heteroduplex than to homoduplex DNA, respectively. No proteins significantly homologous to the two algal G-T binding proteins were found by peptide mass fingerprinting (PMF). The sequence of a peptide generated from trypsin-cleavage of one G-T binding factor (pI 5.5) could be aligned with the amino acid sequences that form the C-terminal active sites of human and mouse mismatch-specific uracil/thymine-DNA glycosylases, suggesting the possibility of this factor as an algae- or a Chlorella-specific DNA mismatch glycosylase.