The Effect of Antihistamines on the Pigments of Green Protista.

SUMMARY. A preliminary survey of the influence of a number of antihistamines on growth of several protozoa indicated that not only growth but also pigment formation in green forms was inhibited. Subsequently, it was demonstrated that molar concentrations of the drugs of less than 1 times 10⁻³ caused chlorosis of cultures of Euglena gracilis var. bacillaris, Chlamydomonas pseudococcum , and Chlorella vulgaris.
With the aid of one of the antihistamines, Pyribenzamine (CIBA), a permanently colorless culture of Euglena was obtained. This culture has been maintained in the chlorotic state in antihistamine-free medium through eighteen serial transfers in constant light. Comparative spectro-photometric studies were made of the pigments extracted from this new euglenid strain with those from normal green, dark-grown and streptomycin-bleached euglenas. Although the dark-etiolated forms retained small amounts of chlorophylls, neither of the drug-bleached cultures showed evidence of these pigments. Quantitatively, the carotenoid picture in dark-bleached and streptomycin-grown organisms was similar, but these pigments were greatly reduced in the Pyribenzamine-treated strain. Further studies on the identity of the carotenoids in the new euglenid are in progress.     

Yellow Pigments of Aspergillus niger and Asp. awamori

From mycelia of Asp. niger and Asp. awamori aurasperones A, B and C along with related two yellow pigments have been isolated.

Aurasperone A, C₃₂H₂₆O₁₀, is obtained in yellow prisms; m.p. 207°C; [α]_d —136°; gives the diacetate and the dimethyl ether and is assumed to be a dimeric 2-methyl-5- hydroxy-6,8-dimethoxy-4H-naphtho [2,3-b] pyran-4-one (IV). Aurasperone B, [α]_D +46.3°, is the main yellow metabolite, m.p. 186°C, and affords aurasperone A on hydrochloric acid-treatment. It has molecular formula C₃₂H₃₀O₁₂ and is supposed to have the structure (V). The other yellow pigments have been found to be also congeners of aurasperone A.     

The Gamete Pigments of Hormosira banksii (Phaeophyta)

The gamete pigments of Hormosira banksii have been separatedby thin-layer chromatography and identified by absorption spectrophotometry.Male gametes contain predominantly ß-carotene, andfemale gametes predominantly chlorophyll and fucoxanthin. Severalminor pigments have also been tentatively identified.     

Pigments of Rubrobacter radiotolerans

The highly radioresistant Rubrobacter radiotolerans, contains red pigments. Since the pigments could not be extracted by usual methods, a new method was developed in which the pigments were extracted with organic solvents after addition of 10 N KOH to the intact cells, followed by neutralization. These pigments were also extracted after treatment with achromopeptidase, but not with lysozyme. The extracted pigments separated into two main spots by TLC (48.6% and 22.6%), and were confirmed to be carotenoids by chemical tests. The two major pigments had 13 conjugated double bonds as determined from the main maximum wavelength of the light absorption spectra. Their molecular weights were determined to be 740 and 722 by mass spectrometry. The mass spectra of their TMS-derivatives revealed that they contained four and three tertiary OH groups, respectively. Confirming their identical light and IR spectra, these pigments were determined to be bacterioruberin and monoanhydrobacterioruberin, respectively, the characteristic carotenoids of halophilic bacteria. The existence of these pigments in bacteria other than halobacteria provides interesting new evidence on the distribution of these compounds.     

The Nature of Melanin Pigments of Several Micro- and Macromycetes

New inhibitors of melanin formation by micromycetes Aspergillus carbonarius, Alternaria alternata, and Paecilomyces variotii and basidiomycetes Inonotus obliquus and Phellinus robustus were found. Precursors of melanin pigments were isolated and identified. p-Hydroxybenzoic acid was identified among the products of alkaline degradation of melanin formed by micromycetes, whereas in the case of macromycetes this was protocatechuic acid. Therefore, melanins of the former were found to belong to the dihydronaphthalene group, whereas those of the latter belong to catechols.     

The Orientation of Rhodopsin and Other Pigments in Dry Films

When rhodopsin in a gelatin film is dried, the rhodopsin chromophores orient primarily in the plane of the film. When the film is wetted, the chromophores disorient. These changes are reversible. When rhodopsin in a wet film. is bleached in the presence of hydroxylamine and redried, the retinal oxime which results is oriented more perpendicularly to the plane of the film. These orientations in dry gelatin films resemble those in the disc membranes of rod outer segments. A variety of other proteins are similarly oriented in dry gelatin films: methemoglobin, cytochrome c, phycocyanin. Films of methemoglobin and cytochrome c display prominently the high Soret band near 410 nm when measured with unpolarized light passing through the face of the fim, but display no Soret band at all with light passing through the edge of the film. All of these orientations imply a large asymmetry of the protein micelles, perhaps conferred upon them by linear polymerization in the course of drying. Such asymmetry can be demonstrated directly with rhodopsin. A wet paste of rhodopsin-digitonin micelles, sheared between glass slides, becomes highly oriented, the rhodopsin chromophores lining up in the direction of shear, the retinal oxime produced by bleaching orienting more perpendicularly to the shear.     

Pigments of Staphylococcus aureus, a series of triterpenoid carotenoids.

The pigments of Staphylococcus aureus were isolated and purified, and their chemical structures were determined. All of the 17 compounds identified were triterpenoid carotenoids possessing a C30 chain instead of the C40 carotenoid structure found in most other organisms. The main pigment, staphyloxanthin, was shown to be alpha-D-glucopyranosyl 1-O-(4,4'-diaponeurosporen-4-oate) 6-O-(12-methyltetradecanoate), in which glucose is esterified with both a triterpenoid carotenoid carboxylic acid and a C15 fatty acid. It is accompanied by isomers containing other hexoses and homologs containing C17 fatty acids. The carotenes 4,4'-diapophytoene, 4,4'-diapophytofluene, 4-4'-diapophytofluene, 4-4'-diapo-zeta-carotene, 4,4'-diapo-7,8,11,12-tetrahydrolycopene, and 4,4'-diaponeurosporene and the xanthophylls 4,4'-diaponeurosporenal, 4,4'-diaponeurosporenoic acid, and glucosyl diaponeurosporenoate were also identified, together with some of their isomers or breakdown products. The symmetrical 4,4'-diapo- structure was adopted for these triterpenoid carotenoids, but an alternative unsymmetrical 8'-apo-structure could not be excluded.     

Biological Role of Xanthomonadin Pigments in Xanthomonas campestris pv. Campestris

Previous studies have indicated that the yellow pigments (xanthomonadins) produced by phytopathogenic Xanthomonas bacteria are unimportant during pathogenesis but may be important for protection against photobiological damage. We used a Xanthomonas campestris pv. campestris parent strain, single-site transposon insertion mutant strains, and chromosomally restored mutant strains to define the biological role of xanthomonadins. Although xanthomonadin mutant strains were comparable to the parent strain for survival when exposed to UV light; after their exposure to the photosensitizer toluidine blue and visible light, survival was greatly reduced. Chromosomally restored mutant strains were completely restored for survival in these conditions. Likewise, epiphytic survival of a xanthomonadin mutant strain was greatly reduced in conditions of high light intensity, whereas a chromosomally restored mutant strain was comparable to the parent strain for epiphytic survival. These results are discussed with respect to previous results, and a model for epiphytic survival of X. campestris pv. campestris is presented.