Evidence for clonal structure of natural populations of free-living amoebae of the genus Naegleria

Abstract

Genetic diversity of natural populations of the two species Naegleria gruberi and N. australiensis collected at the same time in the same area was studied using multilocus enzyme electrophoresis (MLEE analysis). Reference strains and related species were also analysed for comparison. Five loci were found to be polymorphic and allowed identification of 19 different multilocus genotypes among 67 isolates -eight for N. gruberi and 11 for N. australiensis -none being common to the two species. Large departures from Hardy-Weinberg equilibrium were found at all the loci, with significant heterozygote deficiencies in most cases. The two species exhibited strong linkage disequilibrium and the predominance of a few multilocus genotypes within each species was observed. These lines of evidence strongly suggest non-random association of alleles, leading to the conclusion that N. gruberi and N. australiensis have predominantly clonal genetic structures in the wild. Populations consist of a few major clones with some closely related ones -a structure found for several parasitic protozoans and bacteria. This contrasts with the panmictic structure found for N. lo aniensis, another species of this genus, and suggests that closely related species within the genus have evolved to have different reproductive strategies.

Analysis of the 5.8S rRNA Gene and the Internal Transcribed Spacers in Naegleria spp. and in N. fowleri

“…Isoenzyme analysis also revealed that NG260 was separated from the other main Naegleria lineages (Robinson et al 1992). Thus, it is clear that N. gruberi is very heterogeneous as already demonstrated by biochemical and molecular analyses (Clark, Cross, and De Jonckheere 1989; Pernin and Cariou 1997; Robinson et al 1992). In the N. gruberi sample, the results obtained fit well with those of Robinson et al (1992), based on isoenzyme data: strains audl, NG273, and NG206 were phylogenetically closely related.…”

Genetic Variation in the Free-Living AmoebaNaegleria fowleri

“…The wide geographic distribution of some variants could suggest that clonal dispersion occurs. This mode of propagation has been observed for several protozoan organisms (23), including other Naegleria species (22). The similarities between the New Zealand and Australia strains and the Chooz and Cattenom strains (classified as South Pacific and South Pacificlike, respectively) could suggest that they all were derived from a unique ancestral group.…”

Variabilidad genética local del bivalvo dulceacuícola Diplodon chilensis (Gray 1828) proveniente de tres lagos Nahuelbutanos

“…Estudios realizados en la ameba dulceacuícola, Naegleria revelaron vía electroforesis, valores significativos de desequilibrio gamético, los cuales permitieron concluir relevantes aspectos sobre su modo de reproducción (Pernin & Cariou 1997). Los resultados revelaron desequilibrio en las tres poblaciones de Diplodon, es posible que este grupo presente un modo de reproducción alternativo, hermafroditismo facultativo y autofecundación.…”