Caracterização e virulência de bactérias simbiontes de nematoides entomopatogênicos nativos do Brasil, e toxicidade de seus metabolitos secundários para larvas de traça da colméia (Lepidoptera: Pyralidae)

Abstract

Entomopathogenic nematodes (NEPs) comprise an important group of agents used in biological control worldwide. They are found in the soil where they live as infective juvenile (IJ) and search for a host, usually insects that have one or more stages of development on the ground. The IJs carry in their gut an associated bacteria of the genus Xenorhabdus for NEPs of the genus Steinernema, and Photorhabdus to Heterorhabditis. The IJs penetrate the host until the haemocoel, and release the bacterium that recognize L-proline and produce toxins to inhibit the immune system of insects. The bacterium, then, multiplies and the insect dies of septicemia. In this study, 35 strains of Symbiotic bacteria were isolated from native entomopathogenic nematodes indigenous from Brazil, and identified by morphological and biochemical (Tests and API20E API20NE) tests, as well as by molecular test sequencing the 16S rDNA gene. Was also evaluated the toxicity of the bacteria on larvae of Galleria mellonella in three experiments to test cells with Secondary Metabolites (MS), the cell suspension without MS and MS without cells. The bacteria were identified as: X. nematophila (isolates IBCB n2 and IBCB n48), X. doucetiae (IBCB n6, IBSC15, AM47 and AM163), X. magdalenensis (IBCB n28 and AM75), Xenorhabdus sp. (IBCB n34, IBCB n47, IBCB n49, CER17, CER33, CER105, CER107, CER108, CER120, CER144 and CER199), X. szentirmaii (PAM10, PAM11, PAM13, PAM25, PAM31, PAM42, PAM44), X. Romanii (CER09, CER16, CER21, CER129 and CER140), P. luminescens (CB10 and AM71) and P. luminescens subsp akurtsii (IBCB n5). All isolates were pathogenic to G. mellonella in all experiments. Among all promising isolates, only three, P. luminescens subsp akurtsii IBCB n5, X. Romanii CER21 and Xenorhabdus sp. CER106, did not differ significantly from the best isolates in the three experiments (with Cell + MS, MS and cells), which stand out them as the best isolates for use in these ways for the development of products for pest control.