Halobacterium vallismortis sp. nov. An amylolytic and carbohydrate-metabolizing, extremely halophilic bacterium

The extremely halophilic bacterium (formerly designated as strain J.F. 54) isolated from salt pools of the Death Valley, California, is a motile, Gram-negative, extremely pleomorphic organism, aerobe, and facultative anaerobe. A variety of carbohydrates are assimilated with or without acid production; soluble starch is hydrolyzed. The organism is not proteolytic; catalase, oxidase, and DNase reactions are positive; Tween 20 is slightly hydrolyzed, but Tweens 40, 60, and 80 are not. Nitrates are reduced to nitrites with gas production; nitrites are not reduced. Optimum growth temperature is 40 degrees C. Growth is inhibited by bacitracin and by novobiocin. The type strain J.F. 54 differs from described species of the genus Halobacterium and is assigned to a new species, Halobacterium vallismortis sp. nov.

Reduction of trapping of aggregated human IgG in germinal centers by mitogens

The effect of nonspecific mitogens on the trapping of 125I-labeled aggregated human IgG (125I-AHGG) in germinal centers (GC) of mouse spleens has been investigated by both radioactivity uptake and immunofluorescence. Phytohemagglutinin and concanavalin A (Con A) significantly decreased trapping. Lipopolysaccharide produced less inhibition, and pokeweed mitogen had no significant effect. The maximum inhibition occurred with 250--500 mug Con A. This had no effect on 125I-AHGG uptake in liver kidney and blood. No differences were found between i.p. and i.v. routes of Con A injection. The effect of mitogens on the 125I-AHGG trapping in GC is due more likely to modification of the migratory properties of lymphocytes brought about by surface binding, than to their mitogenic properties, since Con A decreased 125I-AHGG localization in thymectomized, x-irradiated and bone marrow-reconstituted animals.

The use of nylon fibre as a method of separating human lymphocyte subpopulations

When the mononuclear cell population separated from normal human blood is passed through a nylon fibre column, monocytes and surface Ig bearing cells are retained; the eluted cells are a mixed properties. It appears that a proportion of the T cells eluted form EA-rosettes, and the eluted cell subpopulation includes non-T cells which share with B cells the ability to bind both EA and aggregated human IgG.

Spontaneous rosette formation by mouse L cells

Mouse fibroblasts form spontaneous rosettes with sheep erythrocytes and with red cells from several other species. They do not form C3 or Fc rosettes, and they do not bind small amounts of aggregated gammaglobulin. Spontaneous rosette formation is maximum at 37 degress and minimum at 4 degrees. The reaction is complete in 30 min. Antisera to fibroblast membrane components do not inhibit rosette formation. Rosetting is inhibited by fixation of the cells with formaldehyde or glutaraldehyde as well as by killing with phenol or by prolonged incubation with sodium azide. The rosette reaction is inhibited by vinblastine but not by cytochalasin B. From these data on the kinetics, temperature and drug sensitivities it is suggested that T cells and fibroblasts form spontaneous rosettes by different mechanisms.

Complement dependence of localisation of aggregated IgG in germinal centres

In vivo decomplementation of mice with cobra factor completely prevented trapping of aggregated human IgG within splenic germinal centres. Observations of the intrasplenic position of the aggregated material within 8 hr of its injection into normal and decomplemented mice suggest that the early phase of localisation in germinal centres depends on binding to lymphocyte C3 receptors.

Interaction of the hinge region of human immunoglobulin G with a murine lymphocyte membrane receptor. Relevance to the problem of antiglobulin induction in rheumatoid arthritis

Evidence is presented which indicates the presence on murine lymphocytes of a membrane receptor for determinants on the hinge region of human IgG. These determinants are exposed following pepsin scission of IgG molecule, i.e. on the F(ab')2 fragment. The evidence for a hinge receptor derives, in vivo, from splenic localization of F(ab')2 in germinal centres and, in vitro, from immunofluorescent binding studies. The sequential immunofluorescent pattern for the uptake of human F(ab)2 fragments into murine spleen germinal centres was identical with that previously observed for heat-aggregated human IgG, but F(ab')2 fragments appeared to be retained in the germinal centres for a shorter time than aggregated IgG. Experiments with nude mice and T cell-deprived mice showed that the localization of F(ab')2 fragments does not require T cells. Competition experiments suggest that the receptor for F(ab')2 may bear little relation to the receptor for aggregated IgG. The relevance of such a lymphocyte membrane receptor to the immunopathology of rheumatoid arthritis is discussed in the light of previous findings that a proportion of the serum IgG of patients with rheumatoid arthritis has a structural anomaly compared with control IgG, characterized exposure of new determinants at the hinge region.

Presence of lipase among species of extremely halophilic bacteria

The presence of lipase in 56 extremely halophilic bacteria was studied by using a plate method with Tweens 20, 40, and 80 as substrates for the enzyme. Thirty-five strains were positive and 21 were negative. Halobacterium salinarium did not hydrolyze any of the Tweens tested. H. cutirubrum hydrolyzed Tween 20 and 40. Micrococcus morrhuae hydrolyzed all Tweens tested. The application of lipase in halobacteria as a taxonomical character was emphasized, and its role in the spoilage of fatty products was considered.