Influence of clay minerals,humic acid and bacterial capsular polysaccharide on the survival of Klebsiella aerogenes exposed to drying and heating in soils

The influence of clay minerals, humic acid and capsular polysaccharide on the survival of Klebsiella aerogenes exposed to drying and heating in soils was investigated. The study of three types of soils showed that the survival of the bacteria was higher in montmorillonitic than in kaolinitic soils. When a sandy soil was amended with 10 per cent montmorillonite, 10 per cent kaolinite or 0.5 per cent humic acid, the survival of K. aerogenes was increased in the presence of montmorillonite but was not affected by kaolinite or humic acid. It was suggested that montmorillinite affected the pattern of water retention by the cells during the drying process. The influence of capsular polysaccharides was also investigated and no significant difference was abserved between the survival of the encapsulated and non-capsulated strains of K. aerogenes exposed to drying and heating in soils. re]19750321     

Effect of montmorillonite and the capsular polysaccharide on the flocculation of Klebsiella aerogenes

A study was undertaken on the effect of colloidal montmorillonite and exocellular polysaccharide produced by Klebsiella aerogenes on the flocculation process of the bacterium.The addition of a low concentration of K-montmorillonite (350 g/ml) led to the flocculation of the non-capsulated strain K₅₄A₃ (0) of K. aerogenes. The volume of the sediment was dependent on the relative concentration of the bacteria and the clay. In contrast with its non-capsulated counterpart, the encapsulated strain K₅₄A₃ was more stable in the presence of a low concentration of K-montmorillonite. The flocculation of the cells was affected by the composition of the growth medium, the suspension being more stable when the bacteria were grown on a rich sugar agar. The addition of capsular polysaccharide to the non-capsulated strain reduced or prevented the flocculation process. These results suggest that the capsular polysaccharide, which contain COO- as sole ionogenic groups, probably attach to and neutralize the positive charges at the edges of the clay platelets. Consequently, K-montmorillonite did not cause any flocculation of the cells when the capsular polysaccharide was present.     

The synthesis of primitive ‘living’ forms: Definitions,goals, strategies and evolution synthesizers

The arbitrariness of the definition of life is discussed in relation to both the archaic biological entities that preceded cells during the Molecular Evolution era, and the hypothetical, primitive, living entities that presumably can be synthesized in the laboratory. Several experimental approaches to the synthesis, detection, and characterization of living entities are discussed. The experimental approaches considered for the synthesis are the constructionist strategy, the whole-environment strategy, and the modular strategy, which is a combination of the first two. The whole-environment strategy is discussed in more detail and the establishment of an Evolution Synthesizer, based on this strategy, is proposed and rationalized. The guidelines for the detection and characterization of populations and processes of living entities include chemical and physical analyses, but are based mainly on the reproductive characterization of these entities. It is expected that the higher the evolutionary level of the living entities, the longer and more difficult it will be to synthesize them, but the easier it will be to detect them.     

Prebiotic nucleotide oligomerization in a fluctuating environment: Effects of kaolinite and cyanamide

Summary The clay kaolinite was tested for its ability to promote nucleotide oligomerization in model prebiotic systems. Heterogeneous mixtures of clay, water and nucleotide were repeatedly evaporated to dryness at 60°C and redissolved in water in cyclic fashion in the presence or absence of cyanamide and/ or ammonium chloride. With or without cycling, kaolinite alone did not promote the oligomerization of nucleotides at detectable levels. Cycling of clay in combination with cyanamide, however, promoted high levels of condensation to a mixture of oligonucleotides and dinucleotide pyrophosphate without requiring ammonium chloride. Although cycling with clay favored synthesis of dinucleotide pyrophosphate, cycling without clay enhanced formation of oligonucleotides. These results support the hypothesis that the presence of clays in fluctuating environments would have influenced the course of prebiotic condensation reactions.     

Suppressor of cytokine signaling 7 inhibits prolactin, growth hormone, and leptin signaling by interacting with STAT5 or STAT3 and attenuating their nuclear translocation

We report here the role of one of the less studied members of the family of suppressors of cytokine signaling (SOCS), namely SOCS-7, in cytokine signaling. We demonstrate that SOCS-7 inhibits prolactin (PRL), growth hormone (GH), or leptin (LEP) signaling mediated through STAT3 and STAT5 in a dose-dependent manner. SOCS-7 also attenuated STAT3 and STAT5 signaling induced by overexpression of JH1, the catalytic subdomain of JAK2. Since SOCS-7 interacted with phosphorylated STAT3 or STAT5, we assumed that SOCS-7 acts at the level of STAT proteins. Indeed, we showed that SOCS-7 inhibits PRL- and leptin-induced STAT5 and STAT3 phosphorylation and prevented the nuclear translocation of activated STAT3. Taken together, our results indicate that SOCS-7 is a physiological dysregulator of PRL, leptin, and probably also GH signaling and that its mode of action is a novel variation of SOCS protein inhibition of cytokine-inducible STAT-mediated signal transduction.     

Increased natural killer cell activity in viremic HIV-1 infection

NK cells are a subset of granular lymphocytes that are critical in the innate immune response to infection. These cells are capable of killing infected cells and secreting integral cytokines and chemokines. The role that this subset of cytolytic cells plays in HIV infection is not well understood. In this study, we dissected the function of NK cells in viremic and aviremic HIV-1-infected subjects, as well as HIV-1-negative control individuals. Despite reduced NK cell numbers in subjects with ongoing viral replication, these cells were significantly more active in secreting both IFN-gamma and TNF-alpha than NK cells from aviremic subjects or HIV-1-negative controls. In addition, NK cells in subjects with detectable viral loads expressed significantly higher levels of CD107a, a marker of lysosomal granule exocytosis. The expression of CD107a correlated with NK cell-mediated cytokine secretion and cytolytic activity as well as with the level of viral replication, suggesting that CD107a represents a good marker for the functional activity of NK cells. Finally, killer Ig-related receptor+ NK cells were stable or elevated in viremic subjects, while the numbers of CD3-/CD56+/CD94+ and CD3-/CD56+/CD161+ NK cells were reduced. Taken together, these data demonstrate that viremic HIV-1 infection is associated with a reduction in NK cell numbers and a perturbation of NK cell subsets, but increased overall NK cell activity.     

Streptococcus iniae type II infections in rainbow trout Oncorhynchus mykiss

Clinical and pathological findings (anorexia, hemorrhage, lethargy, loss of orientation and exophthalmia) indicated that Streptococcus iniae type II is responsible for a fatal disease in rainbow trout. Histopathological findings revealed that S. iniae type II produces a systemic disease, including a diffuse necrotizing myositis. The distribution of viable bacteria in infected tissues substantiated the pathological findings, confirming that S. iniae type II is responsible for a generalized septic disease of rainbow trout.     

High‐resolution definition of humoral immune response correlates of effective immunity against HIV

Defining correlates of immunity by comprehensively interrogating the extensive biological diversity in naturally or experimentally protected subjects may provide insights critical for guiding the development of effective vaccines and antibody‐based therapies. We report advances in a humoral immunoprofiling approach and its application to elucidate hallmarks of effective HIV‐1 viral control. Systematic serological analysis for a cohort of HIV‐infected subjects with varying viral control was conducted using both a high‐resolution, high‐throughput biophysical antibody profiling approach, providing unbiased dissection of the humoral response, along with functional antibody assays, characterizing antibody‐directed effector functions such as complement fixation and phagocytosis that are central to protective immunity. Profiles of subjects with varying viral control were computationally analyzed and modeled in order to deconvolute relationships among IgG Fab properties, Fc characteristics, and effector functions and to identify humoral correlates of potent antiviral antibody‐directed effector activity and effective viral suppression. The resulting models reveal multifaceted and coordinated contributions of polyclonal antibodies to diverse antiviral responses, and suggest key biophysical features predictive of viral control.     

Genetic relationships within avocado (Persea americana Mill) cultivars and between Persea species

The origin of avocado (Persea americana Mill) cultivars, as well as the genetic relationships between Persea species, are not well defined and are based mainly on morphological parameters. Minisatellite DNA markers were used to analyze 24 P. americana cultivars in an attempt to define their racial allocation. DNA mixes representing the three races were evaluated and used for analysis. The allocation of 19 of the above cultivars was substantiated by the DNA markers, while new suggestions were offered regarding the remaining five. Eight cultivars, of unknown racial origin, were also examined, and a phylogenetic tree suggesting their origin is offered. Selfing progeny of five cultivars were analyzed for six morphological traits which differentiate the three races, and were compared to their parents in order to assess their origin. Eleven Persea species were analyzed, using DNA fingerprint patterns and SSR (simple sequence repeat) alleles, in order to identify the genetic relationships among the Persea species, and between them and the three P. americana races. The phylogenetic tree obtained is presented. The high value of variation between the avocado cultivars and Persea species observed in this work, suggests that the validity of race and species definition within Persea be treated with caution. Received: 3 August 1996 / Accepted: 23 August 1996