Person: Gibbs, Karine
Loading...
Email Address
AA Acceptance Date
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
Gibbs
First Name
Karine
Name
Gibbs, Karine
6 results
Search Results
Now showing 1 - 6 of 6
Publication Two Proteins Form a Heteromeric Bacterial Self-Recognition Complex in Which Variable Subdomains Determine Allele-Restricted Binding(American Society of Microbiology, 2015) Cardarelli, Lia; Saak, Christina; Gibbs, KarineABSTRACT Self- versus nonself-recognition in bacteria has been described recently through genetic analyses in multiple systems; however, understanding of the biochemical properties and mechanisms of recognition-determinant proteins remains limited. Here we extend the molecular and biochemical understanding of two recognition-determinant proteins in bacteria. We have found that a heterotypic complex is formed between two bacterial self-recognition proteins, IdsD and IdsE, the genes of which have been shown to genetically encode the determinants for strain-specific identity in the opportunistic bacterial pathogen Proteus mirabilis. This IdsD-IdsE complex forms independently of other P. mirabilis-encoded self-recognition proteins. We have also shown that the binding between IdsD and IdsE is strain- and allele-specific. The specificity for interactions is encoded within a predicted membrane-spanning subdomain within each protein that contains stretches of unique amino acids in each P. mirabilis variant. Finally, we have demonstrated that this in vitro IdsD-IdsE binding interaction correlates to in vivo population identity, suggesting that the binding interactions between IdsD and IdsE are part of a cellular pathway that underpins self-recognition behavior in P. mirabilis and drives bacterial population sociality.Publication The Complete Genome Sequence of Proteus mirabilis Strain BB2000 Reveals Differences from the P. mirabilis Reference Strain(American Society for Microbiology, 2013) Sullivan, Nora L.; Septer, Alecia Noelle; Fields, Andrew T.; Wenren, Larissa; Gibbs, KarineWe announce the complete genome sequence for Proteus mirabilis strain BB2000, a model system for self recognition. This opportunistic pathogen contains a single, circular chromosome (3,846,754 bp). Comparisons between this genome and that of strain HI4320 reveal genetic variations corresponding to previously unknown physiological and self-recognition differences.Publication Identity Gene Expression in Proteus Mirabilis(American Society for Microbiology, 2011) Gibbs, Karine; Wenren, Larissa; Greenberg, E. PeterSwarming colonies of independent Proteus mirabilis isolates recognize each other as foreign and do not merge together, whereas apposing swarms of clonal isolates merge with each other. Swarms of mutants with deletions in the ids gene cluster do not merge with their parent. Thus, ids genes are involved in the ability of P. mirabilis to distinguish self from nonself. Here we have characterized expression of the ids genes. We show that idsABCDEF genes are transcribed as an operon, and we define the promoter region upstream of idsA by deletion analysis. Expression of the ids operon increased in late logarithmic and early stationary phases and appeared to be bistable. Approaching swarms of nonself populations led to increased ids expression and increased the abundance of ids-expressing cells in the bimodal population. This information on ids gene expression provides a foundation for further understanding the molecular details of self-nonself discrimination in P. mirabilis.Publication Two Independent Pathways for Self-Recognition in Proteus Mirabilis Are Linked by Type VI-Dependent Export(American Society for Microbiology, 2013) Wenren, Larissa; Sullivan, N. L.; Cardarelli, L.; Septer, Alecia Noelle; Gibbs, KarineSwarming colonies of the bacterium Proteus mirabilis are capable of self-recognition and territorial behavior. Swarms of independent P. mirabilis isolates can recognize each other as foreign and establish a visible boundary where they meet; in contrast, genetically identical swarms merge. The ids genes, which encode self-identity proteins, are necessary but not sufficient for this territorial behavior. Here we have identified two new gene clusters: one (idr) encodes rhs-related products, and another (tss) encodes a putative type VI secretion (T6S) apparatus. The Ids and Idr proteins function independently of each other in extracellular transport and in territorial behaviors; however, these self-recognition systems are linked via this type VI secretion system. The T6S system is required for export of select Ids and Idr proteins. Our results provide a mechanistic and physiological basis for the fundamental behaviors of self-recognition and territoriality in a bacterial model system.Publication A single point mutation in a TssB/VipA homolog disrupts sheath formation in the type VI secretion system of Proteus mirabilis(Public Library of Science, 2017) Saak, Christina C.; Zepeda-Rivera, Martha A.; Gibbs, KarineThe type VI secretion (T6S) system is a molecular device for the delivery of proteins from one cell into another. T6S function depends on the contractile sheath comprised of TssB/VipA and TssC/VipB proteins. We previously reported on a mutant variant of TssB that disrupts T6S-dependent export of the self-identity protein, IdsD, in the bacterium Proteus mirabilis. Here we determined the mechanism underlying that initial observation. We show that T6S-dependent export of multiple self-recognition proteins is abrogated in this mutant strain. We have mapped the mutation, which is a single amino acid change, to a region predicted to be involved in the formation of the TssB-TssC sheath. We have demonstrated that this mutation does indeed inhibit sheath formation, thereby explaining the global disruption of T6S activity. We propose that this mutation could be utilized as an important tool for studying functions and behaviors associated with T6S systems.Publication The Self-Identity Protein IdsD Is Communicated between Cells in Swarming Proteus mirabilis Colonies(American Society for Microbiology, 2016) Saak, Christina; Gibbs, KarineProteus mirabilis is a social bacterium that is capable of self (kin) versus nonself recognition. Swarming colonies of this bacterium expand outward on surfaces to centimeter-scale distances due to the collective motility of individual cells. Colonies of genetically distinct populations remain separate, while those of identical populations merge. Ids proteins are essential for this recognition behavior. Two of these proteins, IdsD and IdsE, encode identity information for each strain. These two proteins bind in vitro in an allele-restrictive manner. IdsD-IdsE binding is correlated with the merging of populations, whereas a lack of binding is correlated with the separation of populations. Key questions remained about the in vivo interactions of IdsD and IdsE, specifically, whether IdsD and IdsE bind within single cells or whether IdsD-IdsE interactions occur across neighboring cells and, if so, which of the two proteins is exchanged. Here we demonstrate that IdsD must originate from another cell to communicate identity and that this nonresident IdsD interacts with IdsE resident in the recipient cell. Furthermore, we show that unbound IdsD in recipient cells does not cause cell death and instead appears to contribute to a restriction in the expansion radius of the swarming colony. We conclude that P. mirabilis communicates IdsD between neighboring cells for nonlethal kin recognition, which suggests that the Ids proteins constitute a type of cell-cell communication.