Phototactic behaviour of the archaebacterial Natronobacterium pharaonis

Area of Science:

• Microbiology
• Biophysics
• Photobiology

Background:

• Natronobacterium pharaonis exhibits taxis in response to stimuli.
• Cellular movement is facilitated by a monopolarly inserted flagellar bundle.

Purpose of the Study:

• To investigate the mechanism of photophobic response in Natronobacterium pharaonis.
• To identify the specific photoreceptor involved in negative phototaxis.

Main Methods:

• Measuring the photophobic response under sufficient oxygen supply.
• Comparing action spectrum with absorption spectrum of purified psR-II.
• Inhibiting retinal synthesis with nicotine and observing photoresponse changes.

Main Results:

• The action spectrum of the photophobic response matched the absorption spectrum of psR-II.
• Nicotine inhibited retinal synthesis and reduced photoresponse.
• Addition of retinal restored the photoresponse in nicotine-treated cells.

Conclusions:

• psR-II is identified as the receptor mediating negative phototaxis in Natronobacterium pharaonis.
• Retinal synthesis is crucial for the photoresponse mechanism.