Article

Phototaxis and Impaired Motility in Adenylyl Cyclase and Cyclase Receptor Protein Mutants of Synechocystis sp. Strain PCC 6803

Carnegie Institute, Stanford, California, United States
Journal of Bacteriology (Impact Factor: 2.81). 11/2006; 188(20):7306-10. DOI: 10.1128/JB.00573-06
Source: PubMed

ABSTRACT

We have carefully characterized and reexamined the motility and phototactic responses of Synechocystis sp. adenylyl cyclase (Cya1) and catabolite activator protein (SYCRP1) mutants to different light regimens, glucose, 3-(3,4-dichlorophenyl)-1,1-dimethylurea,
and cyclic AMP. We find that contrary to earlier reports, cya1 and sycrp1 mutants are motile and phototactic but are impaired in one particular phase of phototaxis in comparison with wild-type Synechocystis sp.

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Available from: Kenlee Nakasugi
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    • "It is clear that multiple photoreceptors are involved in Synechocystis phototaxis, with light sensors that absorb at different wavelengths and trigger either positive or negative phototaxis (Ng et al., 2004 ). In addition, motility is modulated by the second messengers cyclic diguanylate monophosphate (c-di-GMP) (Savakis et al., 2012) and cyclic adenosine monophosphate (cAMP) (Terauchi and Ohmori, 1999; Bhaya et al., 2006). However, the best-characterized candidate for a directional photoreceptor for positive phototaxis is PixJ1 (also known as TaxD1). "
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    ABSTRACT: Bacterial phototaxis was first recognized over a century ago, but the method by which such small cells can sense the direction of illumination has remained puzzling. The unicellular cyanobacterium Synechocystis sp. PCC 6803 moves with Type IV pili and measures light intensity and color with a range of photoreceptors. Here, we show that individual Synechocystis cells do not respond to a spatiotemporal gradient in light intensity, but rather they directly and accurately sense the position of a light source. We show that directional light sensing is possible because Synechocystis cells act as spherical microlenses, allowing the cell to see a light source and move towards it. A high-resolution image of the light source is focused on the edge of the cell opposite to the source, triggering movement away from the focused spot. Spherical cyanobacteria are probably the world’s smallest and oldest example of a camera eye.DOI: http://dx.doi.org/10.7554/eLife.12620.001
    Full-text · Article · Feb 2016
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    • "They generate cAMP, which is a second messenger that participates in a wide variety of signal transduction systems. In Synechocystis a cya1 knockout has been shown to be impaired in motility [42,43]. The effects of a frameshift mutation in cya1 could be very far reaching however and affect cellular regulation in many ways beyond its motility. "
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    ABSTRACT: Background Temperature tolerance is an important aspect for commercial scale outdoor cultivation of microalgae and cyanobacteria. While various genes are known to be related to Synechocystis sp. PCC6803's heat shock response, there is very limited published data concerning the specific genes involved in long term thermal tolerance. We have previously used random mutagenesis and adaptive evolution to generate a mixture of strains of Synechocystis sp. PCC6803 with significantly increased thermal tolerance. The genetic modifications leading to the phenotypes of the newly generated strains are the focus of this work. Results We used a custom screening platform, based on 96-deepwell microplate culturing in an in house designed cultivation chamber integrated in a liquid handling robot for screening and selection; in addition we also used a more conventional system. The increased thermal tolerances of the isolated monoclonal strains were validated in larger bioreactors and their whole genomes sequenced. Comparison of the sequence information to the parental wild type identified various mutations responsible for the enhanced phenotypes. Among the affected genes identified are clpC, pnp, pyk2, sigF, nlpD, pyrR, pilJ and cya1. Conclusions The applied methods (random mutagenesis, in vivo selection, screening, validation, whole genome sequencing) were successfully applied to identify various mutations, some of which are very unlikely to have been identified by other approaches. Several of the identified mutations are found in various strains and (due to their distribution) are likely to have occurred independently. This, coupled with the relatively low number of affected genes underscores the significance of these specific mutations to convey thermal tolerance in Synechocystis.
    Full-text · Article · Jul 2014 · BMC Biotechnology
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    • "A polyclonal a-Cph2(5-6) antibody was used for detection of Cph2. ses (Bhaya et al., 2006). Wild-type (WT) Synechocystis 6803 cells do not move towards blue light, whereas Dcph2 mutant cells show positive, blue light-dependent phototaxis. "
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    ABSTRACT: Cph2 from the cyanobacterium Synechocystis sp. PCC 6803 is a hybrid photoreceptor that comprises an N-terminal module for red/far-red light reception and a C-terminal module switching between a blue- and a green-receptive state. This unusual photoreceptor exerts complex, light quality-dependent control of the motility of Synechocystis sp. PCC 6803 cells by inhibiting phototaxis towards blue light. Cph2 perceives blue light by its third GAF domain that bears all characteristics of a cyanobacteriochrome (CBCR) including photoconversion between green- and blue-absorbing states as well as formation of a bilin species simultaneously tethered to two cysteines, C994 and C1022. Upon blue light illumination the CBCR domain activates the subsequent C-terminal GGDEF domain, which catalyses formation of the second messenger c-di-GMP. Accordingly, expression of the CBCR-GGDEF module in Δcph2 mutant cells restores the blue light-dependent inhibition of motility. Additional expression of the N-terminal Cph2 fragment harbouring a red/far-red interconverting phytochrome fused to a c-di-GMP degrading EAL domain restores the complex behaviour of the intact Cph2 photosensor. c-di-GMP was shown to regulate flagellar and pili-based motility in several bacteria. Here we provide the first evidence that this universal bacterial second messenger is directly involved in the light-dependent regulation of cyanobacterial phototaxis.
    Full-text · Article · May 2012 · Molecular Microbiology
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