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Quorum sensing influences Vibrio harveyi growth rates in a manner not fully accounted for by the marker effect of bioluminescence.

Nackerdien ZE, Keynan A, Bassler BL, Lederberg J, Thaler DS - PLoS ONE (2008)

Bottom Line: Vh quorum sensing mutants showed altered growth rates that do not always rank with their relative increase or decrease in bioluminescence.In addition, the cell-free culture fluids of a rapidly growing Vibrio parahaemolyticus (Vp) strain increased the growth rate of wild type Vh without significantly altering Vh's bioluminescence.The effect of quorum sensing on Vh growth rate can be either positive or negative and includes both bioluminescence-dependent and independent components.

View Article: PubMed Central - PubMed

Affiliation: Raymond and Beverly Sackler Laboratory of Molecular Genetics and Informatics, Rockefeller University, New York, New York, USA.

ABSTRACT

Background: The light-emitting Vibrios provide excellent material for studying the interaction of cellular communication with growth rate because bioluminescence is a convenient marker for quorum sensing. However, the use of bioluminescence as a marker is complicated because bioluminescence itself may affect growth rate, e.g. by diverting energy.

Methodology/principal findings: The marker effect was explored via growth rate studies in isogenic Vibrio harveyi (Vh) strains altered in quorum sensing on the one hand, and bioluminescence on the other. By hypothesis, growth rate is energy limited: mutants deficient in quorum sensing grow faster because wild type quorum sensing unleashes bioluminescence and bioluminescence diverts energy. Findings reported here confirm a role for bioluminescence in limiting Vh growth rate, at least under the conditions tested. However, the results argue that the bioluminescence is insufficient to explain the relationship of growth rate and quorum sensing in Vh. A Vh mutant for all genes encoding the bioluminescence pathway grew faster than wild type but not as fast as mutants in quorum sensing. Vh quorum sensing mutants showed altered growth rates that do not always rank with their relative increase or decrease in bioluminescence. In addition, the cell-free culture fluids of a rapidly growing Vibrio parahaemolyticus (Vp) strain increased the growth rate of wild type Vh without significantly altering Vh's bioluminescence. The same cell-free culture fluid increased the bioluminescence of Vh quorum mutants.

Conclusions/significance: The effect of quorum sensing on Vh growth rate can be either positive or negative and includes both bioluminescence-dependent and independent components. Bioluminescence tends to slow growth rate but not enough to account for the effects of quorum sensing on growth rate.

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The peak bioluminescence of autoinducer synthase and sensor mutants.Bars represent Relative Light Units (RLU = counts per second/OD) and growth rates (doublings/H; from table 2) are given above each bar. The wild type strains, BB120 and BB866 (WT::Tn5) gave similar RLU values. Wild type RLU values refer to strain BB866 in this figure. Mutant strains: BB152 (luxM), MM30 (luxS), JMH603 (cqsA), JMH634 (luxM, luxS, cqsA), KM664 (luxR), BB170 (luxN), BB886 (luxPQ), JMH598 (cqsS), JMH628 (luxN, luxPQ, cqsS) and BB721 (luxO).
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pone-0001671-g004: The peak bioluminescence of autoinducer synthase and sensor mutants.Bars represent Relative Light Units (RLU = counts per second/OD) and growth rates (doublings/H; from table 2) are given above each bar. The wild type strains, BB120 and BB866 (WT::Tn5) gave similar RLU values. Wild type RLU values refer to strain BB866 in this figure. Mutant strains: BB152 (luxM), MM30 (luxS), JMH603 (cqsA), JMH634 (luxM, luxS, cqsA), KM664 (luxR), BB170 (luxN), BB886 (luxPQ), JMH598 (cqsS), JMH628 (luxN, luxPQ, cqsS) and BB721 (luxO).

Mentions: The quorum sensing mutants under study exhibited expected bioluminescence phenotypes, in keeping with previous findings e.g. the HAI-1-mutant produces 0.3%, the AI-2-mutant produces 3% and the CAI-1-mutant produces 33% of the light produced by the wild type, respectively (see Figure 4). If quorum sensing influenced growth rates primarily through luminescence, bright strains would always grow slowly. Indeed, two mutants exhibited growth defects in keeping with what is known about their luminescence, namely luxO and luxN, luxPQ, cqsS triple mutants (Table 2). These mutants are brighter throughout the exponential phase of growth in contrast to WT , which only reaches the same level of luminescence as these mutants at a high cell density. In addition, these mutants also mimic high cell density states because in both cases, there is no phosphorus flow through the circuit (see Figure 1) [22], [23]. An extension of the energy sink hypothesis is that dim strains might always grow faster in the following order (Figure 4): luxR>luxMluxScqsA>luxM>luxS>cqsA. The atypical growth rates observed for dim strains (Table 2 and Figure 4) can only be partly accounted for by considering signaling strengths. The third autoinducer production/detection system, composed of the autoinducer-sensor pair, CAI-1-CqsS, had previously been shown to have the weakest signaling strength [22], and consistent with this, the growth rates of strains carrying single mutations in this system were essentially unchanged compared to the wild type (see table 2). However, the fastest growth rates were observed for two mutants with opposite luminescence phenotypes and signaling strengths, namely the luxM (HAI-1−, mimics low cell density due to permanent phosphorylation of LuxO by LuxN [9], [22], [23]) and luxN (sensor1-; mimics high cell density due to the lack of phosphorylation of LuxO [9], [22], [23]) mutants (Table 2). A copy of luxM complemented the luminescence (data not shown) but not the growth phenotype (Table 3). Successful complementation of the remaining quorum mutants (Table 3) are consistent with the idea that growth rate changes were consequent to quorum sensing.


Quorum sensing influences Vibrio harveyi growth rates in a manner not fully accounted for by the marker effect of bioluminescence.

Nackerdien ZE, Keynan A, Bassler BL, Lederberg J, Thaler DS - PLoS ONE (2008)

The peak bioluminescence of autoinducer synthase and sensor mutants.Bars represent Relative Light Units (RLU = counts per second/OD) and growth rates (doublings/H; from table 2) are given above each bar. The wild type strains, BB120 and BB866 (WT::Tn5) gave similar RLU values. Wild type RLU values refer to strain BB866 in this figure. Mutant strains: BB152 (luxM), MM30 (luxS), JMH603 (cqsA), JMH634 (luxM, luxS, cqsA), KM664 (luxR), BB170 (luxN), BB886 (luxPQ), JMH598 (cqsS), JMH628 (luxN, luxPQ, cqsS) and BB721 (luxO).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2249925&req=5

pone-0001671-g004: The peak bioluminescence of autoinducer synthase and sensor mutants.Bars represent Relative Light Units (RLU = counts per second/OD) and growth rates (doublings/H; from table 2) are given above each bar. The wild type strains, BB120 and BB866 (WT::Tn5) gave similar RLU values. Wild type RLU values refer to strain BB866 in this figure. Mutant strains: BB152 (luxM), MM30 (luxS), JMH603 (cqsA), JMH634 (luxM, luxS, cqsA), KM664 (luxR), BB170 (luxN), BB886 (luxPQ), JMH598 (cqsS), JMH628 (luxN, luxPQ, cqsS) and BB721 (luxO).
Mentions: The quorum sensing mutants under study exhibited expected bioluminescence phenotypes, in keeping with previous findings e.g. the HAI-1-mutant produces 0.3%, the AI-2-mutant produces 3% and the CAI-1-mutant produces 33% of the light produced by the wild type, respectively (see Figure 4). If quorum sensing influenced growth rates primarily through luminescence, bright strains would always grow slowly. Indeed, two mutants exhibited growth defects in keeping with what is known about their luminescence, namely luxO and luxN, luxPQ, cqsS triple mutants (Table 2). These mutants are brighter throughout the exponential phase of growth in contrast to WT , which only reaches the same level of luminescence as these mutants at a high cell density. In addition, these mutants also mimic high cell density states because in both cases, there is no phosphorus flow through the circuit (see Figure 1) [22], [23]. An extension of the energy sink hypothesis is that dim strains might always grow faster in the following order (Figure 4): luxR>luxMluxScqsA>luxM>luxS>cqsA. The atypical growth rates observed for dim strains (Table 2 and Figure 4) can only be partly accounted for by considering signaling strengths. The third autoinducer production/detection system, composed of the autoinducer-sensor pair, CAI-1-CqsS, had previously been shown to have the weakest signaling strength [22], and consistent with this, the growth rates of strains carrying single mutations in this system were essentially unchanged compared to the wild type (see table 2). However, the fastest growth rates were observed for two mutants with opposite luminescence phenotypes and signaling strengths, namely the luxM (HAI-1−, mimics low cell density due to permanent phosphorylation of LuxO by LuxN [9], [22], [23]) and luxN (sensor1-; mimics high cell density due to the lack of phosphorylation of LuxO [9], [22], [23]) mutants (Table 2). A copy of luxM complemented the luminescence (data not shown) but not the growth phenotype (Table 3). Successful complementation of the remaining quorum mutants (Table 3) are consistent with the idea that growth rate changes were consequent to quorum sensing.

Bottom Line: Vh quorum sensing mutants showed altered growth rates that do not always rank with their relative increase or decrease in bioluminescence.In addition, the cell-free culture fluids of a rapidly growing Vibrio parahaemolyticus (Vp) strain increased the growth rate of wild type Vh without significantly altering Vh's bioluminescence.The effect of quorum sensing on Vh growth rate can be either positive or negative and includes both bioluminescence-dependent and independent components.

View Article: PubMed Central - PubMed

Affiliation: Raymond and Beverly Sackler Laboratory of Molecular Genetics and Informatics, Rockefeller University, New York, New York, USA.

ABSTRACT

Background: The light-emitting Vibrios provide excellent material for studying the interaction of cellular communication with growth rate because bioluminescence is a convenient marker for quorum sensing. However, the use of bioluminescence as a marker is complicated because bioluminescence itself may affect growth rate, e.g. by diverting energy.

Methodology/principal findings: The marker effect was explored via growth rate studies in isogenic Vibrio harveyi (Vh) strains altered in quorum sensing on the one hand, and bioluminescence on the other. By hypothesis, growth rate is energy limited: mutants deficient in quorum sensing grow faster because wild type quorum sensing unleashes bioluminescence and bioluminescence diverts energy. Findings reported here confirm a role for bioluminescence in limiting Vh growth rate, at least under the conditions tested. However, the results argue that the bioluminescence is insufficient to explain the relationship of growth rate and quorum sensing in Vh. A Vh mutant for all genes encoding the bioluminescence pathway grew faster than wild type but not as fast as mutants in quorum sensing. Vh quorum sensing mutants showed altered growth rates that do not always rank with their relative increase or decrease in bioluminescence. In addition, the cell-free culture fluids of a rapidly growing Vibrio parahaemolyticus (Vp) strain increased the growth rate of wild type Vh without significantly altering Vh's bioluminescence. The same cell-free culture fluid increased the bioluminescence of Vh quorum mutants.

Conclusions/significance: The effect of quorum sensing on Vh growth rate can be either positive or negative and includes both bioluminescence-dependent and independent components. Bioluminescence tends to slow growth rate but not enough to account for the effects of quorum sensing on growth rate.

Show MeSH
Related in: MedlinePlus