Ucp-1 from Pantoea Stewartii Affects Bacterial Ultrastructure and Flocculation

Abstract

Aphids are dependent on plants for nutrients and thus their gut microbiome often includes plant pathogens. Recently rhs (rearrangement hotspot) genes, implicated in insect-pathogen interactions, were discovered in the plant pathogen P. stewartii (Stavrinides et al. (2010) Environmental Microbiology 12, 147-155.). In P. stewartii, the rhs gene product, named Ucp-1 (youcannot pass 1), is responsible for conferring flocculating behaviour in the gut of the pea aphid, Acyrthosiphon pisum, ultimately resulting in its death. Absence of the gene in P. stewartii, gives rise to a mutant that is non-flocculating and non-lethal to the aphid, and transfer of the gene to Escherichia coli transforms it into a flocculating pathogen of aphids. Here we use atomic force microscopy (AFM) and force spectroscopy (FS) to study the flocculating patterns, and cell surface ultrastructure, physical and chemical properties of wild type and E. coli cloned and over-expressing one of seven Ucp1-like proteins from the Pantoea genome. The Ucp-1 mutant, capable of transforming E. coli into a flocculating pathogen, has a distinct aggregation pattern and cell surface ultrastructure.