17 research outputs found
N. elongata Produces Type IV Pili That Mediate Interspecies Gene Transfer with N. gonorrhoeae
The genus Neisseria contains at least eight commensal and two pathogenic species. According to the Neisseria phylogenetic tree, commensals are basal to the pathogens. N. elongata, which is at the opposite end of the tree from N. gonorrhoeae, has been observed to be fimbriated, and these fimbriae are correlated with genetic competence in this organism. We tested the hypothesis that the fimbriae of N. elongata are Type IV pili (Tfp), and that Tfp functions in genetic competence. We provide evidence that the N. elongata fimbriae are indeed Tfp. Tfp, as well as the DNA Uptake Sequence (DUS), greatly enhance N. elongata DNA transformation. Tfp allows N. elongata to make intimate contact with N. gonorrhoeae and to mediate the transfer of antibiotic resistance markers between these two species. We conclude that Tfp functional for genetic competence is a trait of a commensal member of the Neisseria genus. Our findings provide a mechanism for the horizontal gene transfer that has been observed among Neisseria species
Shaping the growth behaviour of biofilms initiated from bacterial aggregates
Bacterial biofilms are usually assumed to originate from individual cells
deposited on a surface. However, many biofilm-forming bacteria tend to
aggregate in the planktonic phase so that it is possible that many natural and
infectious biofilms originate wholly or partially from pre-formed cell
aggregates. Here, we use agent-based computer simulations to investigate the
role of pre-formed aggregates in biofilm development. Focusing on the initial
shape the aggregate forms on the surface, we find that the degree of spreading
of an aggregate on a surface can play an important role in determining its
eventual fate during biofilm development. Specifically, initially spread
aggregates perform better when competition with surrounding unaggregated
bacterial cells is low, while initially rounded aggregates perform better when
competition with surrounding unaggregated cells is high. These contrasting
outcomes are governed by a trade-off between aggregate surface area and height.
Our results provide new insight into biofilm formation and development, and
reveal new factors that may be at play in the social evolution of biofilm
communities
Vibrio cholerae use pili and flagella synergistically to effect motility switching and conditional surface attachment.
We show that Vibrio cholerae, the causative agent of cholera, use their flagella and mannose-sensitive hemagglutinin (MSHA) type IV pili synergistically to switch between two complementary motility states that together facilitate surface selection and attachment. Flagellar rotation counter-rotates the cell body, causing MSHA pili to have periodic mechanical contact with the surface for surface-skimming cells. Using tracking algorithms at 5 ms resolution we observe two motility behaviours: 'roaming', characterized by meandering trajectories, and 'orbiting', characterized by repetitive high-curvature orbits. We develop a hydrodynamic model showing that these phenotypes result from a nonlinear relationship between trajectory shape and frictional forces between pili and the surface: strong pili-surface interactions generate orbiting motion, increasing the local bacterial loiter time. Time-lapse imaging reveals how only orbiting mode cells can attach irreversibly and form microcolonies. These observations suggest that MSHA pili are crucial for surface selection, irreversible attachment, and ultimately microcolony formation