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Bacterial secretion and the role of diffusive and subdiffusive first passage processes.

Marten F, Tsaneva-Atanasova K, Giuggioli L - PLoS ONE (2012)

Bottom Line: By funneling protein effectors through needle complexes located on the cellular membrane, bacteria are able to infect host cells during type III secretion events.As a result, theoretical predictions of secretion times are still lacking.Here we provide a model that quantifies, depending on the transport characteristics within bacterial cytoplasm, the amount of time for a protein effector to reach either of the available needle complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom.

ABSTRACT
By funneling protein effectors through needle complexes located on the cellular membrane, bacteria are able to infect host cells during type III secretion events. The spatio-temporal mechanisms through which these events occur are however not fully understood, due in part to the inherent challenges in tracking single molecules moving within an intracellular medium. As a result, theoretical predictions of secretion times are still lacking. Here we provide a model that quantifies, depending on the transport characteristics within bacterial cytoplasm, the amount of time for a protein effector to reach either of the available needle complexes. Using parameters from Shigella flexneri we are able to test the role that translocators might have to activate the needle complexes and offer semi-quantitative explanations of recent experimental observations.

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Related in: MedlinePlus

Isobars of the spatially averaged mean first passage time  of a Brownian particle in a sphere with radius  and  targets on the boundary, as a function of target radius  and diffusion coefficient .Its respective values (in seconds) along each isobar are shown by text labels. The parameter  is set to  in all plots; hence we assume that the particle can start its motion from anywhere in the domain. Left to right: , 42 and 92. Row (A):  is fixed to 0.5 m. Row (B):   = 1.1 m.
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pone-0041421-g005: Isobars of the spatially averaged mean first passage time of a Brownian particle in a sphere with radius and targets on the boundary, as a function of target radius and diffusion coefficient .Its respective values (in seconds) along each isobar are shown by text labels. The parameter is set to in all plots; hence we assume that the particle can start its motion from anywhere in the domain. Left to right: , 42 and 92. Row (A): is fixed to 0.5 m. Row (B):  = 1.1 m.

Mentions: By solving the associated matricial equation (see Eq. (1.1)–(1.3) in Supporting Information S1) in Fig. 5 we show values of as function of target radius and diffusion coefficient for different numbers of needle complexes (targets) and under the assumption that effectors can start from anywhere in the sphere . The various panels are isobars of as function of target radius and diffusion coefficient for different numbers of needle complexes and two values of the bacterium radius, m in the top panels and m in the bottom panels. By sequentially looking at panels A-B-C or D-E-F, it is evident that decreases as function of . Alternatively, Fig. 5 can be used to estimate what value of diffusion constant is required to ensure a certain effector arrival time at any of the needle complexes. For example, an arrival time of 100 seconds when  = 1.1 m,  = 92 and  = 100 Å (Fig. 5F) requires the diffusion coefficient to be 0.01 m/s, whereas needs to be 1 m/s if  = 0.5 m and there is only one target of radius  = 10 Å (Fig. 5A). For any , the relative simplicity of the expression (3) shows that to any of the values plotted in Fig. 5 one needs to rescale the result with the appropriate and add the quantity .


Bacterial secretion and the role of diffusive and subdiffusive first passage processes.

Marten F, Tsaneva-Atanasova K, Giuggioli L - PLoS ONE (2012)

Isobars of the spatially averaged mean first passage time  of a Brownian particle in a sphere with radius  and  targets on the boundary, as a function of target radius  and diffusion coefficient .Its respective values (in seconds) along each isobar are shown by text labels. The parameter  is set to  in all plots; hence we assume that the particle can start its motion from anywhere in the domain. Left to right: , 42 and 92. Row (A):  is fixed to 0.5 m. Row (B):   = 1.1 m.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3412870&req=5

pone-0041421-g005: Isobars of the spatially averaged mean first passage time of a Brownian particle in a sphere with radius and targets on the boundary, as a function of target radius and diffusion coefficient .Its respective values (in seconds) along each isobar are shown by text labels. The parameter is set to in all plots; hence we assume that the particle can start its motion from anywhere in the domain. Left to right: , 42 and 92. Row (A): is fixed to 0.5 m. Row (B):  = 1.1 m.
Mentions: By solving the associated matricial equation (see Eq. (1.1)–(1.3) in Supporting Information S1) in Fig. 5 we show values of as function of target radius and diffusion coefficient for different numbers of needle complexes (targets) and under the assumption that effectors can start from anywhere in the sphere . The various panels are isobars of as function of target radius and diffusion coefficient for different numbers of needle complexes and two values of the bacterium radius, m in the top panels and m in the bottom panels. By sequentially looking at panels A-B-C or D-E-F, it is evident that decreases as function of . Alternatively, Fig. 5 can be used to estimate what value of diffusion constant is required to ensure a certain effector arrival time at any of the needle complexes. For example, an arrival time of 100 seconds when  = 1.1 m,  = 92 and  = 100 Å (Fig. 5F) requires the diffusion coefficient to be 0.01 m/s, whereas needs to be 1 m/s if  = 0.5 m and there is only one target of radius  = 10 Å (Fig. 5A). For any , the relative simplicity of the expression (3) shows that to any of the values plotted in Fig. 5 one needs to rescale the result with the appropriate and add the quantity .

Bottom Line: By funneling protein effectors through needle complexes located on the cellular membrane, bacteria are able to infect host cells during type III secretion events.As a result, theoretical predictions of secretion times are still lacking.Here we provide a model that quantifies, depending on the transport characteristics within bacterial cytoplasm, the amount of time for a protein effector to reach either of the available needle complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom.

ABSTRACT
By funneling protein effectors through needle complexes located on the cellular membrane, bacteria are able to infect host cells during type III secretion events. The spatio-temporal mechanisms through which these events occur are however not fully understood, due in part to the inherent challenges in tracking single molecules moving within an intracellular medium. As a result, theoretical predictions of secretion times are still lacking. Here we provide a model that quantifies, depending on the transport characteristics within bacterial cytoplasm, the amount of time for a protein effector to reach either of the available needle complexes. Using parameters from Shigella flexneri we are able to test the role that translocators might have to activate the needle complexes and offer semi-quantitative explanations of recent experimental observations.

Show MeSH
Related in: MedlinePlus