The evolution of human chromosome 21: evidence from in situ hybridization in marsupials and a monotreme.

We have mapped five human chromosome 21 (HSA 21) markers in marsupials and a monotreme, two major groups of mammals that diverged from eutherians 130-150 and 150-170 million years before present (MYrBP), respectively. We have found that these genes map to two distinct autosomal sites, one containing SOD1/CBR/BCEI and the other containing ETS2/INFAR, in the marsupials Macropus eugenii and Sminthopsis macroura (which belong to orders that diverged 40-80 MYrBP), as well as in the monotreme Ornithorhynchus anatinus (the platypus). Since marsupials and monotremes diverged independently from eutherians, these data suggest that HSA 21 genes were originally located in two separate autosomal blocks. In another Sminthopsis species, SOD1 is linked to TRF (a marker on HSA 3q), suggesting that the ancestral SOD1/CBR/BCEI region also included HSA 3 markers. We suggest that these blocks became fused early in the eutherian evolution to form a HSA 3/21 chromosome, which has remained intact in artiodactyls, but has been independently disrupted in both the primate and rodent lineages.     

Nitrospira marina gen. nov. sp. nov.: a chemolithotrophic nitrite-oxidizing bacterium

A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine. N. marina is a Gramnegative curved rod which may form spirals with 1 to 12 turns. Cells have a unique periplasmic space and lack intracytoplasmic membranes and carboxysomes. N. marina is an obligate chemolithotroph, but best growth is obtained in a mixotrophic medium. N. marina may be one of the most prevalent nitrite-oxidizing bacteria in some oceanic environments. Type strain is field with American Type Culture Collection (ATCC 43039).     

The action of nitrous acid on C-teichoic acid (C-substance) from the walls of Diplococcus pneumoniae

1. C-teichoic acid (C-substance) from the walls of Diplococcus pneumoniae contained free amino groups accessible to attack by nitrous acid. Treatment with nitrous acid, followed by reduction with borohydride and hydrolysis with acid, gave ribitol, glucitol and their respective phosphates. 2. Hydrolysis of the polymer with alkali followed by treatment of products with nitrous acid yielded glucose. 3. When alkali hydrolysis was followed by treatment with a phosphomonoesterase, nitrous acid degradation of C-substance yielded glucose and a disaccharide identified as 2-O-(N-acetylgalactosaminyl)-d-ribitol. 4. A partial structure for C-teichoic acid was deduced in which the order of the constituent residues and the position of phosphodiester linkages were established.     

Respiratory Components of Aspergillus niger Mitochondria

The respiratory components of tightly coupled mitochondria from the filamentous fungus Aspergillus niger were studied. Cytochromes a + a(3), b, and c + c(1) were identified by difference spectra. The cytochrome spectra were qualitatively similar to yeast and rat liver mitochondria. The mitochondria contained, per gram of protein, an average of 2.9 and 7.0 mumoles of ubiquinone and nicotinamide adenine dinucleotide, respectively.     

Properties of substituted 2-trifluoromethylbenzimidazoles as uncouplers of oxidative phosphorylation

1. The activity of 25 substituted 2-trifluoromethylbenzimidazoles in uncoupling oxidative phosphorylation by rat-liver mitochondria has been compared. 2. For halogen- or mixed-halogen- and alkyl-substituted analogues, uncoupling activity was proportional to the acidity of the imidazole -NH group. Tetrachloro-2-trifluoromethylbenzimidazole was the most active (50% uncoupling of oxidative phosphorylation at 7.9x10(-8)m, pK5.04). Nitro-substituted analogues were less active than predicted from pK considerations or from partition-coefficient measurements. 3. Introduction of an -NH(2) or -CO(2)H substitutent caused a loss of uncoupling activity, as did alkylation at position 1 of the imidazole ring. 4. Benzimidazoles active as uncouplers stimulated mitochondrial adenosine triphosphatase but not all stimulated the oxidation of succinate in the absence of a phosphate acceptor. 5. 4,5-Dichloro-2-trifluoromethylbenzimidazole inhibited the succinate-oxidase system at about the same concentration required for uncoupling (0.52mum for 50% inhibition of both activities) and the site of this inhibition appears to lie between succinate dehydrogenase and cytochrome b.