Evaluation of five antibiotics on larval gut bacterial diversity of Plutella xylostella (Lepidoptera: Plutellidae)

Abstract

Larvae of the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), have rich microbial communities inhabiting the gut, and these bacteria contribute to the fitness of the pest. In this study we evaluated the effects of five antibiotics (rifampicin, ampicillin, tetracycline, streptomycin sulfate and chloramphenicol) on the gut bacterial diversity of P. xylostella larvae. We screened five different concentrations for each antibiotic in a leaf disc assay, and found that rifampicin and streptomycin sulfate at 3 mg/mL significantly reduced the diversity of the bacterial community, and some bacterial species could be rapidly eliminated. The number of gut bacteria in the rifampicin group and streptomycin sulfate group decreased more rapidly than the others. With the increase of antibiotic concentration, the removal efficiency was improved, whereas toxic effects became more apparent. All antibiotics reduced larval growth and development, and eventually caused high mortality, malformation of the prepupae, and hindered pupation and adult emergence. Among the five antibiotics, tetracycline was the most toxic and streptomycin sulfate was a relatively mild one. Some dominant bacteria were not affected by feeding antibiotics alone. Denaturing gradient gel electrophoresis graph showed that the most abundant and diverse bacteria in P. xylostella larval gut appeared in the cabbage feeding group, and diet change and antibiotics intake influenced gut flora abundance. Species diversity was significantly reduced in the artificial diet and antibiotics treatment groups. After feeding on the artificial diet with rifampicin, streptomycin sulfate and their mixture for 10 days, larval gut bacteria could not be completely removed as detected with the agarose gel electrophoresis method.

Metagenomic Sequencing of Diamondback Moth Gut Microbiome Unveils Key Holobiont Adaptations for Herbivory

“…This lepidopteran is difficult to control because it has developed resistance to most classes of insecticides (Baxter et al, 2005; Zalucki et al, 2012). Many studies have focused on the bacterial diversity of the P. xylostella gut based on culturing and denaturing gradient gel electrophoresis (DGGE) methods (Indiragandhi et al, 2007; Lin et al, 2015a,b) but these only partially reveal the gut microbial diversity. Our previous study based on the sequencing of V6 region of 16S rRNA supplied a more complete understanding of the P. xylostella gut microbiota than earlier culturing-based studies (Xia et al, 2013).…”

Evidence for a conserved microbiota across the different developmental stages of Plodia interpunctella

“…In most of the cases, microbiota investigation highlighted interesting host-symbiont interactions, representing key aspects in insect's survival and adaptation, such as development, nutrition, detoxification, and maintaining of the immune system (Dillon & Dillon, 2004;Engel & Moran, 2013). Regarding lepidopterans, the studies on their bacterial communities have increased in the recent years, especially for insect pest moths such as Ostrinia nubilalis (Belda et al, 2011), Spodoptera littoralis (Tang et al, 2012), Lymantria dispar (Broderick et al, 2004;Lin et al, 2015), Helicoverpa armigera (Xiang et al, 2006), Plutella xylostella (Xia et al, 2013), and Bombyx mori (Liang et al, 2014). Furthermore, some of these studies revealed the role played by the bacteria in helping the host in a broad range of activities.…”

The microbiome of pest insects: it is not just bacteria

“…Another approach that can be used to experimentally manipulate components of the bacterial microbiome is the use of (cocktails of) antibiotics that target specific bacterial groups, or temperature-shock treatments that affects some microbes more than others. With these approaches, the microbiome changes in composition, and the performance of insects can be compared with vs. without, or among different combinations of treatments (Bordenstein & Bordenstein, 2011;Lin et al, 2015). Although these methods provide an indication of potential links between microbiome and host, these are usually mere correlations and should therefore be interpreted with caution, as they might not infer causation.…”