ABSTRACT
The fluorescent amplified fragment length polymorphism (FAFLP) groups A5 (21 isolates), A8 (6 isolates) and A23 (3 isolates) distinguished in an earlier paper (Thompson et al., Syst Appl Microbiol 24, 520-538, 2001) were examined in more depth. These three groups were phylogenetically related to Vibrio tubiashii, but DNA-DNA hybridization experiments proved that the three AFLP groups are in fact novel species. Chemotaxonomic and phenotypic analyses further revealed several differences among the 30 isolates and known Vibrio species. It is proposed to accommodate these isolates in three novel species, namely Vibrio neptunius (type strain LMG 20536T; EMBL accession no. AJ316171; G +C content of the type strain 46.0 mol%), Vibrio brasiliensis (type strain LMG 20546T; EMBL accession no. AJ316172; G + C content of the type strain 45.9 mol%) and Vibrio xuii (type strain LMG 21346T; EMBL accession no. AJ316181; G +C content of the type strain 46.6 mol%). These species can be differentiated on the basis of phenotypic features, including fatty acid composition (particularly 14:0 iso, 14:0 iso 3-OH, 16:0 iso, 16:0, 17:0 and 17:1 omega8c), enzyme activities and utilization and fermentation of various carbon sources.
Subject(s)
Vibrio/classification , Vibrio/isolation & purification , Animals , Aquaculture , Base Composition , Crustacea/microbiology , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/genetics , Fatty Acids/analysis , Fishes/microbiology , Molecular Sequence Data , Nucleic Acid Amplification Techniques , Phenotype , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , Rotifera/microbiology , Species Specificity , Vibrio/genetics , Vibrio/metabolismABSTRACT
Chromocentres, i.e. heavily stainable heterochromatic areas with highly repetitive DNA (a 130-bp repeat in the order of 6 x 105 copies per haploid genome) observed in the resting nucleus, are a reliable taxonomic trait and a good marker for speciation in Artemia. This chromosome marker was evaluated in populations of two New World sibling species: A. franciscana, from North, Central and South America, and A. persimilis from Argentina. Artemia persimilis showed the characteristically low average chromocentre numbers (<3) of the ancestral Mediterranean species, whilst higher numbers (>5) were seen in A. franciscana. The increase in chromocentre numbers from A. persimilis to A. franciscana occurred in a rather steady, continuous geographical pattern with an overlapping zone between both species. A north-south steady latitudinal decline of chomocentres was observed towards the equator in A. franciscana populations from the northern hemisphere, whilst the trait increased from this point towards southern latitudes with a population in Chilean Patagonia (below 52 degrees S) exhibiting the highest chromocentre frequency. Since chromocentres are positively correlated with repetitive DNA content, differentiation between the species through the amplification of heterochromatin or an increased DNA content in A. franciscana (although this species has a lower diploid chromosome number), might nevertheless reflect chromosomal reorganizations between the species. Chromocentres, together with other traits, reveal a probable hybrid zone between the two species in Chilean Patagonia.