Abstract
Xenorhabdus nematophila, an entomopathogenic bacterium that symbiotically associates with the entomoparasitic nematode Steinernema carpocapsae, was studied to determine its physiological parameters of glucose utilization. X. nematophila was cultured in chemically defined media containing various concentrations of glucose under optimal conditions utilizing a two-liter fermentation system. Specific growth rates were obtained from each glucose batch. Specific growth rates and their associated glucose concentrations were used to determine physiological parameters. These parameters include the bacterium's substrate utilization constant (K s) and its maximum specific growth rate (μ max). The bacteria exhibited a K s value of 2.02 mg/L suggesting that X. nematophila has a high affinity for glucose. The μ max of Xenorhabdus was determined to be 1.03 h−1. Further research is needed to determine if microbial affinities to different substrates have any influence on biological relationships (symbiosis, pathogenicity, parasitism, etc.) between prokaryotes and higher organisms.
Highlights
Xenorhabdus nematophila is a Gram-negative, rod shaped, endosymbiotic bacterium found exclusively within the gut of the entomoparasitic nematode Steinernema carpocapsae
In order to mass produce entomoparasitic nematodes in vitro, it is crucial to understand the physiology of the bacterial symbiont to various substrates that are found within insect hemolymph and potential nematode growth media
The present study is the initiation of understanding the physiological nature of the entomopathogenic bacterium X. nematophila in regard to glucose utilization within the insect hemolymph
Summary
Xenorhabdus nematophila is a Gram-negative, rod shaped, endosymbiotic bacterium found exclusively within the gut of the entomoparasitic nematode Steinernema carpocapsae. Due to the pair’s interesting biological characteristics, they have become model organisms for studying nematode symbiosis, host-bacterium interactions, and parasitism [3]. These nematode-bacterial complexes are mass produced and commercialized for use as biological insecticides [4, 5]. Once the nematode gains access to the insect hemolymph, regurgitation of its symbiotic bacteria occurs It is inside of the hemolymph where bacteria proliferation occurs. In order to mass produce entomoparasitic nematodes in vitro, it is crucial to understand the physiology of the bacterial symbiont to various substrates that are found within insect hemolymph and potential nematode growth media. Physiological constants of X. nematophila such as the substrate utilization constant (Ks) and maximum specific growth rate (μmax) were determined
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