Light-Induced Lysis and Carotenogenesis inMyxococcus xanthus

Abstract

BURCHARD, ROBERT P. (University of Minnesota, Minneapolis), AND MARTIN DWORKIN. Light-induced lysis and carotenogenesis in Myxococcus xanthus. J. Bacteriol. 91:535-545. 1966.-Myxococcus xanthus, grown vegetatively in the light, developed an orange carotenoid after the cells entered stationary phase of growth; pigment content increased with age. Cells grown in the dark did not develop carotenoid and could be photolysed by relatively low-intensity light only during stationary phase; rate of photolysis increased with age. Photolysis adhered to the reciprocity law, was temperature-independent and oxygen-dependent, and required the presence of nonspecific, monovalent cations; it was inhibited by one of several divalent cations. Logarithmic-phase cells were photosensitized by 100,000 X g pellet preparations of sonic-treated stationary-phase cells grown in the light and dark. A porphyrin with a Soret band at 408 m,u was isolated from photosensitive cells; logarithmic-phase cells contained about 1X6 the amount of porphyrin of stationary-phase cells. The purified material had spectral and chemical properties of protoporphyrin IX and photosensitized logarithmic-phase cells. Its spectrum was similar to the action spectrum for photolysis. We concluded that protoporphyrin IX is the natural endogenous photosensitizer. Carotenogenesis was stimulated by light in the blue-violet region of the visible spectrum and was inhibited by diphenylamine, resulting in photosensitivity of the cells. Photoprotection by carotenoid was lost in the cold. A mutant which synthesized carotenoid in the light and dark was photosensitive only after growth in diphenylamine. The ecological significance of these phenomena is discussed.

Light‐induced carotenogenesis in Myxococcus xanthus: DNA sequence analysis of the carR region

“…Carotenoids are capable of quenching both singlet oxygen and many triplet-state photosensitive molecules. In M. xanthus the photosensitizing molecule for carotenogenesis and photolysis appears to be protoporphyrin IX, the precursor or primary breakdown product of haem (Burchard et al, 1966;Burchard and Hendricks, 1969). Burchard and Dworkin (1966) reported that the site of action of light damage in carotenoid-lacking cells of M. xanthus was the membrane.…”

Changes in Myxococcus xanthus pigments induced by phosphate and temperature

“…It is known that the biosynthesis of various secondary products (pigments, antibiotics, alkaloids) is influenced by temperature and phosphate levels (Weinberg 1974;Martin & Demain 1980). At least one of the functions of the pigments in myxobacteria is to prevent photolysis (Burchard & Dworkin 1966). It has also been proposed that the carotenoids might serve as structural elements and stabilizers for the membrane (Reichenbach & Kleinig 1984) and in fact the addition of phosphate to the medium, which lowered the pigment content in the strains DK101, DK1050, DK718, MR7 and MR151 also stimulated their autolysis.…”

“…These pigments consist of a mixture of highly unsaturated, acyclic and monocyclic carotenoids (Reichenbach & Kleinig 1984). Carotenogenesis in myxobacteria has been shown to be controlled by both physiological and environmental factors; thus carotenogenesis in Myxococcus xanthus is stimulated in many cases, but not always, by light (Kleinig & Reichenbach 1973) and is dependent on the presence of a photosensitizer (Burchard & Dworkin 1966). Genetic elements have also been identified as being involved in the control of carotenogenesis (Martinez-Laborda et al 1986;Martinez-Laborda & Murillo 1989).…”

“…Genetic elements have also been identified as being involved in the control of carotenogenesis (Martinez-Laborda et al 1986;Martinez-Laborda & Murillo 1989). In addition to carotenoids, myxobacteria contain other pigments, particularly a yellow one, which predominates in dark-grown cells of Myxococcus xanthus (Burchard & Dworkin 1966). Inorganic phosphate and temperature are known to suppress the biosynthesis of pigments in other micro-organisms (Martin & Demain 1980).…”

Effect of light on germinating spores of Streptomyces viridosporus

“…The damaging e¡ects of light on microbial cells, components and activities have been reported in several studies: lysis on agar of Myxococcus xanthus with protoporphyrin IX, identi¢ed as the blue light photoreceptor for photolysis [1]; irreversible paralysis of Salmonella typhimurium and Escherichia coli [2]; dormancy and loss of culturability in E. coli in a freshwater ecosystem mediated by visible light [3,4] and growth inhibition of methanogens by light in the blue end of the visible spectrum [5].…”