Chemotactic Behavior of Pathogenic and Nonpathogenic Leptospira Species

Institut Pasteur, Unité de Biologie des Spirochètes, Paris, France.
Applied and Environmental Microbiology (Impact Factor: 3.67). 12/2012; 78(23). DOI: 10.1128/AEM.02288-12


We have developed a capillary tube assay in combination with real-time PCR to quantitate the number of chemoattracted Leptospira cells. We identified Tween 80, glucose, sucrose, and pyruvate as attractants for Leptospira cells; amino acids and vitamin B12 were found to be nonchemotactic or weakly chemotactic. This assay has the general applicability to further our understanding
of leptospiral chemotaxis.

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    • "Accumulation of Leptospira cells near the agar drop To confirm the chemotactic behaviour of L. biflexa cells towards agar that contained an attractant, we first performed MAA using glucose and sucrose. Both these sugars are known to induce positive chemotactic responses in L. biflexa (Lambert et al., 2012b). When the agar contained no sugar, the cells did not accumulate near the agar drop (Fig. 2). "
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    ABSTRACT: Chemotaxis allows bacterial cells to migrate towards or away from chemical compounds. In the present study, we developed a microscopic agar-drop assay (MAA) to investigate the chemotactic behaviour of a coiled spirochete, Lepto-spira biflexa. An agar drop containing a putative attractant or repellent was placed around the centre of a flow chamber and the behaviour of free-swim-ming cells was analysed under a microscope. MAA showed that L. biflexa cells gradually accumulated around an agar drop that contained an attractant such as glucose. Leptospira cells often spin without migration by transformation of their cell body. The frequency at which cells showed no net displacement decreased with a higher glucose concentration, suggesting that sensing an attractive chemical allows these cells to swim more smoothly. Investigation of the chemotactic behaviour of these cells in response to different types of sugars showed that fructose and mannitol induced negative chemotactic responses, whereas xylose and lactose were non-chemotactic for L. biflexa. The MAA developed in this study can be used to investigate other chemoattractants and repellents.
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    ABSTRACT: The mechanisms of disease pathogenesis in leptospirosis are poorly defined. Recent developments in the application of genetic tools in the study of Leptospira have advanced our understanding by allowing the assessment of mutants in animal models. As a result, a small number of essential virulence factors have been identified, though most do not have a clearly defined function. Significant advances have also been made in the in vitro characterization of leptospiral interaction with host structures, including extracellular matrix proteins (such as laminin, elastin, fibronectin, collagens), proteins related to hemostasis (fibrinogen, plasmin), and soluble mediators of complement resistance (factor H, C4b-binding protein), although none of these in vitro findings has been translated to the host animal. Binding to host structures may permit colonization of the host, prevention of blood clotting may contribute to hemorrhage, while interaction with complement resistance mediators may contribute to survival in serum. While not a classical intracellular pathogen, the interaction of leptospires and phagocytic cells appears complex, with bacteria surviving uptake and promoting apoptosis; mutants relating to these processes (such as cell invasion and oxidative stress resistance) are attenuated in vivo. Another feature of leptospiral biology is the high degree of functional redundancy and the surprising lack of attenuation of mutants in what appear to be certain virulence factors, such as LipL32 and LigB. While many advances have been made, there remains a lack of understanding of how Leptospira causes tissue pathology. It is likely that leptospires have many novel pathogenesis mechanisms that are yet to be identified.
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