Occurrence of natural dixenic associations between the symbiont Photorhabdus luminescens and bacteria related to Ochrobactrum spp. in tropical entomopathogenic Heterorhabditis spp. (Nematoda, Rhabditida) The EMBL accession numbers for the 16S rDNA sequences reported in this paper are AJ245941 (PR17/sat), AJ249458 (FRG11/sat) and AJ249459 (DO23/sat).

Abstract

Bacteria naturally associated with the symbiont Photorhabdus luminescens subsp. akhurstii were isolated from the entomopathogenic nematode Heterorhabditis indica. Bacterial isolates distinct from P. luminescens subsp. akhurstii were obtained from 33 % of the samples. Fourteen bacterial isolates, from nematodes collected from three different Caribbean islands, were characterized by conventional phenotypic tests, restriction fragment length polymorphism and sequence analyses of PCR-amplified 16S rRNA genes (16S rDNAs). Isolates were grouped into three genotypes, each one being associated with one Caribbean island. Phenotypic characteristics and 16S rDNA analysis showed that the Photorhabdus-associated bacteria were closely related to Ochrobactrum anthropi for the group from Guadeloupe, and to Ochrobactrum intermedium for the two groups from the Dominican Republic and Puerto Rico. No pathogenicity of the Ochrobactrum spp. to the insects Galleria mellonella and Spodoptera littoralis (Lepidoptera) was detected. Since Ochrobactrum spp. are considered as human opportunist pathogens, the mass production of entomopathogenic nematodes for biological control requires strict vigilance.

A novel symbiotic nitrogen-fixing member of the Ochrobactrum clade isolated from root nodules of Acacia mangiu

“…The strains DASA 35030, DASA 35082 and PDA-1 were aligned with the sequences of the type strains of the 70 known species belonging to the families Rhizobiaceae, Phyllobacteriaceae, Bartonellaceae, Brucellaceae and Bradyrhizobiaceae, and the strain PR17/sat of Ochrobactrum sp. isolated from a nematode (Babic et al, 2000), that were obtained from DNA databases. On the phylogenetic tree constructed on the basis of the aligned 16S rRNA sequences, the strain DASA 35030 was placed in Ochrobactrum/Brucella clade within the family Brucellaceae.…”

Specificity of Association between Paenibacillus spp. and the Entomopathogenic Nematodes, Heterorhabditis spp.

“…strains which were found associated with Heterorhabditis spp. were resistant to Photorhabdus antibiotics [4,18]. When tested in vitro, the three nematode-associated Paenibacillus strains were shown to be resistant to Photorhabdus, unlike other species of Paenibacillus including the closely related P. azoreducens.…”

“…Providencia rettgeri was isolated from several strains following prolonged laboratory culture [18], whereas Ochrobactrum spp. were found naturally associated with one third of newly isolated H. indica from the Caribbean [4]. In both of these studies the nematodes were surface sterilized, but not desheathed, prior to isolation of the bacteria [4,18]; hence, the bacteria were carried either in the intestine or between the sheath and the living cuticle.…”

Effects of Paenibacillus nematophilus on the entomopathogenic nematode Heterorhabditis megidis

“…(Babic et al, 2000). In both of these studies the IJs were surface sterilized, but not desheathed, prior to isolation of the bacteria, hence the bacteria were carried either in the intestine, or between the sheath and the living cuticle (Babic et al, 2000;Jackson et al, 1995). No adverse eVects of either Providencia or Ochrobactrum on Heterorhabditis have been reported.…”

“…Non-symbiont bacteria reported in association with Heterorhabditis include Providencia rettgeri (Jackson et al, 1995) and Ochrobactrum spp. (Babic et al, 2000). In both of these studies the IJs were surface sterilized, but not desheathed, prior to isolation of the bacteria, hence the bacteria were carried either in the intestine, or between the sheath and the living cuticle (Babic et al, 2000;Jackson et al, 1995).…”