Article Abstract:
The entomopathogenic bacteria Photorhabdus luminescens contains two yellow pigments, anthraquinone derivatives and the antibiotic 3,5-dihydroxy-4-isopropylstilbene. The pigments 3,8-dimethoxy-1-hydroxy-9,10-anthraquinone and 1,3-dimethoxy-8-hydroxy-9,10-anthraquinone are present in a ratio of 1:3. They have antimicrobial activity and act as antagonistic agents against other microorganisms in the insect the bacteria infects. The antibiotic has strong fungicidal activity against many fungi.
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Article Abstract:
Low osmolarity seems to cause the bacterium Photorhabdus luminescens to shift from its primary to its secondary phase. When in the secondary phase, this bacterium stimulates propogation of the nematodes whose intestines it occupies symbiotically. Other environmental factors, such as light, pH, temperature, and oxygen levels do not seem to elicit a phase shift. However, light, oxygen depletion, and extreme pH made the primary phase less stable.
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Article Abstract:
Research was conducted to characterize a small-colony variant (Vsm) of the primary form (Vp) of Photorhabdus luminescens MD (enterobacteriaceae) in vitro and in vivo. The Vsm variant was not the preferred food of its nematode symbiont, was found not to support the development and reproduction of the nematode and was less pathogenic than Vp to Galleria mellonella larvae. Results indicate that the nematode preferred Vp over Vsm.
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