Lukasz M. Tymo

A symbiotic bacterium, strain IMI 397775^T, was isolated from the insect-pathogenic nematode Steinernema australe. On the basis of 16S rRNA gene sequence similarity, this bacterial isolate was shown to belong to the genus Xenorhabdus , in agreement with the genus of its nematode host. The accurate phylogenetic position of this new isolate was defined using a multigene approach and showed that isolate IMI 397775^T shares a common ancestor with Xenorhabdus doucetiae FRM16^T and Xenorhabdus romanii PR06-A^T, the symbiotic bacteria associated with Steinernema diaprepesi and Steinernema puertoricense, respectively. The nucleotide identity (less than 97 %) between isolate IMI 397775^T, X. doucetiae FRM16^T and X. romanii PR06-A^T calculated for the concatenated sequences of five gene fragments encompassing 4275 nt, several phenotypic traits and the difference between the upper temperatures that limit growth of these three bacteria allowed genetic and phenotypic differentiation of isolate IMI 397775^T from the two closely related species. Strain IMI 397775^T therefore represents a novel species, for which the name Xenorhabdus magdalenensis sp. nov. is proposed, with the type strain IMI 397775^T ( = DSM 24915^T).

A systematic programme of surveys for entomopathogenic nematodes (EPN) was done in Chile between 2006 and 2008. The survey spanned the principal ecosystems of mainland Chile as well as a number of islands, and covered a wide range of habitats including the Atacama Desert, Andean Altiplano, temperate rainforests and subpolar territory. Nearly 1400 soil samples were collected, of which 7% were positive for EPN. Of 101 EPN isolates obtained, 94 were Steinernema spp. and seven were Heterorhabditis sp. Of the 94 Steinernema isolates, 39 were identified as Steinernema feltiae, the remainder being distributed between two new species, S. unicornum (52 records) and S. australe (three records). The Heterorhabditis isolates, all designated as Heterorhabditis sp.1, are referred to herein as H. cf. safricana. Steinernema feltiae and S. unicornum were collected predominately in the south of Chile and were obtained from a range of habitats, including forests, open grassland, montane soils and coastal zones; neither species was recovered from the far north of the country (viz., desert soils in the Norte Grande region). Steinernema australe was found in only three soil samples, all from humid, cool, coastal localities in the south. Heterorhabditis cf. safricana was recovered from the northern regions, with most isolates found in or on the periphery of the Atacama Desert; they were not recovered from cooler, more humid regions of southern Chile. Molecular information indicated there were two subgroups of both S. unicornum and S. feltiae, with a geographical, intraspecific split of subgroups between the most southerly and the more central survey zones. All isolates were collected by ex situ baiting with waxmoth larvae and the natural hosts are unknown.

A new species of entomopathogenic nematode, Steinernema australe n. sp., was isolated from a soil sample taken close to the beach on Isla Magdalena, an island in the Pacific Ocean, 2 km from mainland Chile. Morphologically the new species belongs to the glaseri-group and is characterised by morphometrics of the infective juvenile which has a very long body of 1316 (1162-1484) μm, excretory pore located far posterior to the anterior extremity (110 (95-125) μm), exceptionally long tail of 103 (92-114) μm, H% = 51 (42-61), E% = 107 (94-122) and a ratio = 35 (31-38). The first generation male has 72 (55-78) μm long spicules, a 45 (36-51) μm long gubernaculum and SW% = 172 (118-196). The first generation female can be recognised by well developed double epiptygmata, the lack of a prominent postanal swelling, a mucron on the tail tip and (in 60% of individuals) one to two subsidiary mucrons. Sequences of the ITS and D2D3 regions of the ribosomal DNA confirm that S. australe n. sp. is a valid species.