Studies on nodule formation in locusts following injection of microbial products

The ability of various bacterial cell wall components to induce nodule formation was tested in the locusts, Locusta migratoria and Schistocerca gregaria. Peptidoglycan, particularly the lysozymesoluble fragment, was found to be responsible for the nodule formation elicited by preparations of Micrococcus luteus cell wall. Once extracted, however, the lysozyme-soluble peptidoglycan fragments did not elicit nodules. Isolated teichoic acid extracted from the wall of Staphylococcus aureus also failed to induce nodules. Its removal from cell wall preparations, however, enhanced their ability to trigger nodule formation. A range of Escherichia coli lipopolysaccharide mutants was also tested but there was no clear role for lipopolysaccharide in the nodule formation process. A commercial lipopolysaccharide preparation tested failed to elicit nodule formation. Finally, the role of capsular polysaccharides was examined using a capsulate parent and a noncapsulate mutant strain of Klebsiella pneumoniae. The presence of capsule on the parent strain and capsular material isolated from this strain gave significant enhancement of nodule formation. The results presented are discussed in comparison with the ability of these microbial components to activate prophenoloxidase in vitro. This comparison shows, in the majority of cases, a positive link between prophenoloxidase activation and nodule formation.