Phylogeography of the invasive cyanobacterium Cylindrospermopsis raciborskii

Abstract

Cylindrospermopsis raciborskii is a planktonic freshwater cyanobacterium that has become increasingly prevalent in tropical and temperate water bodies world-wide. This species is of concern from a water-quality perspective because of its known ability to produce toxins that can affect the health of humans and other animals. This study investigates genetic variation between strains of C. raciborskii isolated from freshwater rivers and reservoirs in Australia, Brazil, Germany, Hungary, Portugal and the USA. Strains were first characterized by analysis of their 16S rRNA gene nucleotide sequences and were found to have a sequence divergence of 99.1%. A phylogenetic tree, constructed using the 16S rRNA gene sequences showed that strains grouped into Australian, European and North/South American phylotypes. To investigate further the observed separation of strains into geographically distinct groups, we applied a cyanobacterium-specific short tandem repeat sequence technique, HIP1. An electrophoretic comparison of the HIP1 polymerase chain reaction products showed clear distinctions between the C. raciborskii strains. A phylogenetic tree, based on the repeat element banding patterns, also revealed three distinct groups of C. raciborskii strains. The first group consisted of strains from the USA and Brazil; the second comprised European strains from Germany, Hungary and Portugal; and the third were strains from Australia. In general, between-country variation was greater than within-country variation, indicating that this fingerprinting technique can successfully distinguish C. raciborskii strains taken from different global locations. The relationship between toxicity and the observed HIP1 polymerase chain reaction fingerprint profiles was less clear, although it is interesting to note that of the strains analysed in this study, only Australian strains are known to produce cylindrospermopsin and only Brazilian strains have been reported to produce paralytic shellfish poisoning toxins.

Recent occurrence ofCylindrospermopsis raciborskiiin Waikato lakes of New Zealand

“…It is also known to be capable of producing paralytic shellfish poisoning (PSP) (Lagos et al 1999;Neilan et al 2003). In a review of the cyanotoxin cylindrospermopsin, Griffiths & Saker (2003) describe recent developments in the application of molecular techniques for characterising strains of cyanobacteria that produce this toxin.…”

A rapid microbiotest for the detection of cyanobacterial toxins

“…The explanation for the differences in the toxic levels found with the two microbiotests for the same cyanobacterial species (samples 13 and 14) is hence probably due to a different mechanism of toxicity induction by the Hungarian strain versus the Australian strain, with the Rapidtoxkit being very sensitive to the toxin(s) produced by the former. Neilan et al (2003) already reported the existence of three different phylogeographical groups of C. raciborskii strains collected from different parts of the globe on the base of HIP1 polymerase chain reaction fingerprint profile. He found that there was no relationship between the toxicity and the HIP1 polymerase chain reaction fingerprint profile, although paralytic shellfish poison and cylindrospermopsin producing strains were examined and at the same time no known toxins were found in European strains either.…”

Seasonal morphological variability in an in situ Cyanobacteria monoculture: example from a persistent Cylindrospermopsis bloom in Lake Catemaco, Veracruz, Mexico

“…These morphologies occur in other lakes (Bouvy et al, 1999;Neilan et al, 2003;Padisak, 2003), and maintain their identity through generations in culture with no transitional forms ). The circular trichomes may be either complete and partially overlapping circles or semi-circles.…”

“…However, for the genus, there is considerable confusion about what defines a species, and the amount of strain level variability differs depending on the genetic region compared. Previous studies have shown that C. raciborskii originating from different parts of the world share nucleotide similarities of ≥99.1% for 16S rRNA, ≥98% for rpoC1, ≥97.5% for nifH, ≥94.5% for cpcBA intergenic spacer (cpcBA-IGS), and ≥91% for 16S-23S internal transcribed spacer region (ITS1) (Dyble et al, 2002;Neilan et al, 2003;Gugger et al, 2005). Compared to global variability, genetic sequence analysis of Lake Catemaco samples during different years and seasons consistently show very high genetic similarity.…”