Polyphasic identification of cyanobacterial isolates from Australia

Area of Science:

• Environmental microbiology
• Molecular biology
• Aquatic ecology

Background:

• Cyanobacterial blooms impact water quality and safety, necessitating reliable species identification.
• Traditional morphological identification methods have limitations, leading to the adoption of molecular techniques.
• Polyphasic approaches combining microscopy and DNA-based analyses are increasingly used for cyanobacterial identification.

Purpose of the Study:

• To compare morphological and molecular characterizations of Australian cyanobacterial isolates.
• To assess the reliability of current identification methods for cyanobacteria.
• To identify novel cyanobacterial genotypes and evaluate sequence data quality in GenBank.

Main Methods:

• Morphological characterization of 39 cyanobacterial isolates.
• DNA sequencing of 16S ribosomal RNA gene (16S rDNA), RNA polymerase gene (rpoC1), and phycocyanin operon (cpcBA-IGS).
• Phylogenetic analysis to determine cyanobacterial orders and identify novel genotypes.

Main Results:

• Phylogenetic analyses identified three orders: Chroococcales, Oscillatoriales, and Nostocales.
• 22% of strains exhibited <95% similarity to existing GenBank sequences, indicating novel genotypes.
• Agreement between morphological and molecular data was low: 26% at species level and 31% at genus level.

Conclusions:

• Despite advances in molecular tools, confident cyanobacteria identification remains challenging.
• Limitations include unreliable morphological features, culture-induced pleomorphism, and poor quality of GenBank sequences.
• Further improvements in taxonomic standards and data curation are needed for reliable cyanobacterial identification.