Isolation and characterization of two novel plasmids pCYM01 and pCYM02 of Cylindrospermum stagnale

Cyanobacteria play a vital role in supplying nitrogen into the soil and aquatic ecosystem. It has an extra chromosomal DNA, whose role is not yet defined well. Isolation and characterization of extra chromosomal DNA in cyanobacteria might help to understand its survival mechanism. Cylindrospermum stagnale isolated (and deposited in NRMCF 3001) from soil showed presence of four plasmids namely pCYLM01, pCYLM02, pCYLM03, and pCYLM04. The following plasmids pCYLM01 and pCYLM02 were subjected to restriction digestion using HindIII restriction enzyme and cloned into pBlueScriptSK(-) vector. The sequence of pCYLM01 contained 4 potential open reading frames (ORFs) that have amino acids in the range of 59–299. Among them, ORF1 shows high sequence homology to the bacterial replication initiator family protein as evident from BLASTP analysis. The analysis of 4359 bp plasmid pCYLM02 sequence revealed 7 ORFs which are longer than 50 amino acids in length. The ORF2 of pCYLM02 has 243 amino acids and is represented in the plasmid sequence from 3045 to 3776 bp. The ORF3 of pCYLM02 corresponds to the plasmid sequence from 2323 to 2976 and codes for a putative protein of 217 amino acids long. A number of small ORFs below 50 bp were also found in the sequence analysis.