Real-time PCR as an effective technique to assess the impact of phoresy by Paenibacillus sp. bacteria on Steinernema diaprepesi nematodes in nature.
Quantitative real-time PCR (qPCR) is a powerful tool to study species of cryptic organisms in complex food webs. This technique was recently developed to detect and quantify several species of entomopathogenic nematodes (EPNs), which are widely used for biological control of insects, and some natural enemies of EPNs such as nematophagous fungi and the phoretic bacteria Paenibacillus sp. and Paenibacillus nematophilus. A drawback to the use of primers and TaqMan probes designed for Paenibacillus sp. is that the qPCR also amplified Paenibacillus thiaminolyticus and Paenibacillus popilliae, two closely related species that are not phoretically associated with EPNs. Here, we report that the detection of Paenibacillus sp. DNA in nematode samples was two orders of magnitude greater (P < 0.001) when the bacterium was added to soil together with its EPN species-specific host Steinernema diaprepesi than when it was added concomitantly with other EPNs or with species of bacterial-feeding nematodes. Just 6% of samples detected trace amounts of P. thiaminolyticus and P. popilliae exposed to the same experimental conditions. Thus, although the molecular assay detects Paenibacillus spp. DNA in nonphoretic associations, the levels are essentially background compared to the detection of Paenibacillus sp. in association with its nematode host.
Entomology and Nematology Department, Citrus Research and Education Center, University of Florida, IFAS, 700 Experiment Station Road, Lake Alfred, FL 33850-2299, USA. r.camposherrera@ufl.edu
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Campos-Herrera
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El-Borai
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Duncan
D000818:Animals; D017931:DNA Primers / Q000235:genetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D056507:Paenibacillus / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D017168:Rhabditida / Q000382:microbiology* / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013559:Symbiosis
D017931:DNA Primers; D015345:Oligonucleotide Probes