Electrostatic charge controls the lowest LH1 Qy transition energy in the triply extremophilic purple phototrophic bacterium, Halorhodospira halochloris

Kimura, Yukihiro; Nojima, Shingo; Nakata, Kazuna; Yamashita, Takuya; Wang, Xiangping; Takenaka, Shinji; Akimoto, Seiji; Kobayashi, Masayuki; Madigan, Michael T.; Wang-Otomo, Zheng-Yu; Yu, Long-Jiang

doi:10.1016/j.bbabio.2021.148473

Cited by 12 publications

(31 citation statements)

References 49 publications

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“…The salt-dependent and interconvertible spectral changes of the Hlr. halochloris LH1-RCs were largely comparable to those reported previously [ 25 ] but were significantly different from those observed for the mesophilic Hlr. abdelmalekii LH1-RCs, as shown in Figure 1 B.…”

Section: Resultssupporting

confidence: 73%

“…The pH-dependent spectral changes were interconvertible, not only for Hlr. halochloris ( Figure 1 D) [ 25 , 26 ] but also for Hlr. abdelmalekii ( Figure 1 E).…”

Section: Resultsmentioning

confidence: 99%

“…abdelmalekii ) at various pHs ( Figure 1 F). The salt- and pH-dependent spectral changes of these Halorhodospira species were nonspecific to coexisting ion species and their valences [ 25 ], and distinct from the Ca 2+ -specific spectral changes of several BChl a-containing purple sulfur bacteria, including Tch. tepidum [ 27 ], Alc.…”

Section: Resultsmentioning

confidence: 99%

“…halochloris strain DSM 1059 and Hlr. abdelmalekii strain DSM 2110 were grown photosynthetically (anoxic/light) at 43 °C and 28 °C, respectively, under illumination of a 60 W incandescent lamp for 7–10 days in the medium of Imhoff and Trüper [ 3 ] with slight modifications [ 25 ]. The harvested cells suspended in 20 mM Tris-HCl buffer (pH 8.5) were disrupted by sonication (Sonopuls HD3200, Bandelin, Berlin, Germany) and ultracentrifuged at 195,000× g for 60 min (L60, Beckman) to obtain photosynthetic membranes (chromatophores).…”

Section: Methodsmentioning

confidence: 99%

“…In a previous study, we reported salt- and pH-sensitive interconvertible LH1 Q y band shifts of the purified LH1-RC complex from Hlr. halochloris [ 25 ] and demonstrated that the native spectral properties of the LH1-RC were maintained in the presence of high concentrations of salts and/or at alkaline pH (>7). During these experiments, it was observed that lowering the salt concentration and/or the pH induced Q y blue-shifts and decreased the band intensities, suggesting that the thermal stability of the Hlr.…”

Section: Introductionmentioning

confidence: 99%

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Salt- and pH-Dependent Thermal Stability of Photocomplexes from Extremophilic Bacteriochlorophyll b-Containing Halorhodospira Species

et al. 2022

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Halorhodospira (Hlr.) species are the most halophilic and alkaliphilic of all purple bacteria. Hlr. halochloris exhibits the lowest LH1 Qy transition energy among phototrophic organisms and is the only known triply extremophilic anoxygenic phototroph, displaying a thermophilic, halophilic, and alkaliphilic phenotype. Recently, we reported that electrostatic charges are responsible for the unusual spectroscopic properties of the Hlr. halochloris LH1 complex. In the present work, we examined the effects of salt and pH on the spectroscopic properties and thermal stability of LH1-RCs from Hlr. halochloris compared with its mesophilic counterpart, Hlr. abdelmalekii. Experiments in which the photocomplexes were subjected to different levels of salt or variable pH revealed that the thermal stability of LH1-RCs from both species was largely retained in the presence of high salt concentrations and/or at alkaline pH but was markedly reduced by lowering the salt concentration and/or pH. Based on the amino acid sequences of LH1 polypeptides and their composition of acidic/basic residues and the Hofmeister series for cation/anion species, we discuss the importance of electrostatic charge in stabilizing the Hlr. halochloris LH1-RC complex to allow it to perform photosynthesis in its warm, hypersaline, and alkaline habitat.

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Section: Resultssupporting

confidence: 73%

“…The pH-dependent spectral changes were interconvertible, not only for Hlr. halochloris ( Figure 1 D) [ 25 , 26 ] but also for Hlr. abdelmalekii ( Figure 1 E).…”

Section: Resultsmentioning

confidence: 99%