Streptomyces youssoufiensis sp. nov., isolated from a Moroccan phosphate mine.

A novel actinomycete, strain X4(T), was isolated from a phosphate mine in Youssoufia, 100 km north of Marrakesh, Morocco. The taxonomic status of this strain was evaluated by a polyphasic approach. Strain X4(T) had white aerial mycelium with Rectiflexibiles spore chains bearing smooth-surfaced spores and did not produce diffusible pigments. Chemotaxonomic analysis showed that the cell wall of strain X4(T) contained LL-diaminopimelic acid and glycine. Phylogenetic analysis based on the almost complete 16S rRNA gene sequence indicated that strain X4(T) belongs to the Group I streptomycetes, branching off next to Streptomyces ramulosus NRRL B-2714(T) and Streptomyces kasugaensis M338-M1(T). DNA-DNA relatedness and phenotypic data enabled strain X4(T) to be distinguished from the phylogenetically most closely related type strains. It is therefore proposed that strain X4(T) represents a novel species of the genus Streptomyces, for which the name Streptomyces youssoufiensis sp. nov. is proposed; the type strain is X4(T) ( = CCMM B709(T)  = DSM 41920(T)).

Streptomyces thinghirensis sp. nov., isolated from rhizosphere soil of Vitis vinifera.

A novel actinomycete, strain S10(T), was isolated from rhizosphere soil of wild Vitis vinifera in Thinghir, Ouarzazate Province, Southern Morocco. The taxonomic status of this strain was established using a polyphasic approach. Strain S10(T) had white-grey aerial mycelium with long, spiral spore chains bearing smooth surfaced spores and produced a yellow diffusible pigment. Chemotaxonomic analyses showed that the cell wall of strain S10(T) contained ll-diaminopimelic acid and glycine. Phylogenetic analysis based on the almost complete 16S rRNA gene sequence indicated that strain S10(T) belonged to the Group I streptomycetes, branching off next to Streptomyces marokkonensis LMG 23016(T) from the Streptomyces violaceoruber group. DNA-DNA relatedness and phenotypic data distinguished strain S10(T) from the phylogenetically closest related type strains. It is therefore proposed that strain S10(T) (=CCMM B35(T)=DSM 41919(T)) represents the type strain of a novel species of the genus Streptomyces, for which the name Streptomyces thinghirensis sp. nov. is proposed.

Identification of intramembrane hydrogen bonding between 13(1) keto group of bacteriochlorophyll and serine residue alpha27 in the LH2 light-harvesting complex.

Intramembrane hydrogen bonding and its effect on the structural integrity of purple bacterial light-harvesting complex 2, LH2, have been assessed in the native membrane environment. A novel hydrogen bond has been identified by Raman resonance spectroscopy between a serine residue of the membrane-spanning region of LH2 alpha-subunit, and the C-13(1) keto carbonyl of bacteriochlorophyll (BChl) B850 bound to the beta-subunit. Replacement of the serine by alanine disrupts this strong hydrogen bond, but this neither alters the strongly red-shifted absorption nor the structural arrangement of the BChls, as judged from circular dichroism. It also decreases only slightly the thermal stability of the mutated LH2 in the native membrane environment. The possibility is discussed that weak H-bonding between the C-13(1) keto carbonyl and a methyl hydrogen of the alanine replacing serine(-4) or the imidazole group of the nearby histidine maintains structural integrity in this very stable bacterial light-harvesting complex. A more widespread occurrence of H-bonding to C-13(1) not only in BChl, but also in chlorophyll proteins, is indicated by a theoretical analysis of chlorophyll/polypeptide contacts at <3.5 A in the high-resolution structure of Photosystem I. Nearly half of the 96 chlorophylls have aa residues suitable as hydrogen bond donors to their keto groups.