FEMS Microbiology Letters, 362, 2015, fnu063 doi: 10.1093/femsle/fnu063 Advance Access Publication Date: 23 December 2014 Research Letter R E S E A R C H L E T T E R – Environmental Microbiology Presence of calcium-binding motifs in PilY1 homologs correlates with Ca-mediated twitching motility and evolutionary history across diverse bacteria Jennifer K. Parker, Luisa F. Cruz, Michael R. Evans and Leonardo De La Fuente ∗ Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, USA ∗ Corresponding author: Department of Entomology and Plant Pathology, 209 Rouse Life Sciences Bldg., Auburn University, Auburn, AL 36849, USA. Tel: +334-844-2582; Fax: +334-844-1947; E-mail: lzd0005@auburn.edu One sentence summary: Increase in twitching motility in response to calcium is restricted to bacteria containing a specifc calcium-binding motif in a protein associated with type IV pili. Editor: Ross Fitzgerald ABSTRACT Twitching motility, involving type IV pili, is essential for host colonization and virulence of many pathogenic bacteria. Studies of PilY1, a tip-associated type IV pili protein, indicate that PilY1 functions as a switch between pilus extension and retraction, resulting in twitching motility. Recent work detected a calcium-binding motif in PilY1 of some animal bacterial pathogens and demonstrated that binding of calcium to PilY1 with this motif regulates twitching. Though studies of PilY1 in non-animal pathogens are limited, our group demonstrated that twitching motility in the plant pathogen Xylella fastidiosa, which contains three PilY1 homologs, is increased by calcium supplementation. A study was conducted to investigate the phylogenetic relationship between multiple PilY1 homologs, the presence of calcium-binding motifs therein, and calcium-mediated twitching motility across diverse bacteria. Strains analyzed contained one to three PilY1 homologs, but phylogenetic analyses indicated that PilY1 homologs containing the calcium-binding motif Dx[DN]xDGxxD are phylogenetically divergent from other PilY1 homologs. Plant-associated bacteria included in these analyses were then examined for a calcium-mediated twitching response. Results indicate that bacteria must have at least one PilY1 homolog containing the Dx[DN]xDGxxD motif to display a calcium-mediated increase in twitching motility, which likely refects an adaption to environmental calcium concentrations. Key words: calcium; bacteria; twitching; type IV pili; pilY1 homologs INTRODUCTION Twitching motility, generated by type IV pili (TFP) extension and retraction, is crucial for host colonization and other virulence traits in many bacteria (Mattick 2002; Burdman et al., 2011; Bur- rows 2012). Through extension, attachment and retraction, TFP produce a motile force which pulls cells forward (Merz, So and Sheetz 2000; Mattick 2002). A variety of Gram-negative bacte- ria display twitching motility, including the animal pathogens Pseudomonas aeruginosa (Burrows 2012), Neisseria meningitidis (Al- biger, Johansson and Jonsson 2003; Morand et al., 2004), N. gonorrhoeae (Kallstrom et al., 1998; Wolfgang et al., 1998) and Kingella kingae (Porsch et al., 2013), and the plant pathogens Ralstonia solanacearum (Liu et al., 2001), Xylella fastidiosa (Meng et al., 2005), Acidovorax citrulli (Bahar, Goffer and Burdman 2009), Xanthomonas spp. (Ojanen-Reuhs et al., 1997; Su et al., 1999; Wang Received: 22 October 2014; Accepted: 19 December 2014 C  FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com 1 Downloaded from https://academic.oup.com/femsle/article-abstract/362/4/1/535915 by guest on 27 May 2020