Salmonella–Macrophage Interactions upon Manganese Supplementation

Various studies indicate the role of manganese (Mn) in the virulence of pathogens. Salmonella is an intracellular pathogen which is able to multiply within the macrophages. The present study was therefore, designed to assess the effect of Mn supplementation on Salmonella–macrophage interactions particularly in reference to Salmonella virulence and macrophage functions. A 50-fold decrease in the lethal dose 50 (LD₅₀) of Salmonella typhimurium was observed when mice were infected with Salmonella grown in the presence of Mn as compared to the LD₅₀ in the absence of Mn indicating an increase in the virulence of the organism. A significant increase was observed in the levels of superoxide dismutase (SOD) of S. typhimurium grown in presence of manganese. Upon Mn supplementation, macrophage functions were also found to be altered. Decreased phagocytic activity of macrophages interacted with Salmonella was observed in presence of Mn as compared to the activity in the absence of Mn. A significant increase was observed in the extent of lipid peroxidation along with significant decreases in the activities of SOD and catalase as well as nitrite levels of macrophages interacted with S. typhimurium upon supplementation with Mn. These observations indicate that Mn supplementation might have increased the expression of Mn transporters in Salmonella resulting in increased levels of its superoxide dismutase. The altered Salmonella function in turn might have been responsible for inhibiting phagocytosis and impairing the balance between the oxidant and antioxidant profile of macrophages, thus protecting itself by exhibiting exalted virulence.     

Native trees of the Northeast Argentine: Natural hosts of the Cryptococcus neoformans–Cryptococcus gattii species complex

BackgroundIn Argentina, information about epidemiology and environmental distribution of Cryptococcus is scarce. The city of Resistencia borders with Brazil and Paraguay where this fungus is endemic. All these supported the need to investigate the ecology of the genus and the epidemiology of cryptococcosis in this area.AimsThe aim was to investigate the presence of species of Cryptococcus neoformans–Cryptococcus gattii complex and their genotypes in trees of the city of Resistencia.MethodsOne hundred and five trees were sampled by swabbing technique. The isolates were identified using conventional and commercial methods and genotyped by PCR-RFLP (Restriction Fragment Length Polymorphism).ResultsCryptococcus was found in 7 out of the total trees. 6 out of 7 Cryptococcus isolates were identified as C. neoformans and one as C. gattii. C. gattii was isolated from Grevillea robusta. C. neoformans strains were isolated from Tabebuia avellanedae and Peltophorum dubium. Genotyping showed that all C. neoformans belonged to the VNI type and C. gattii belonged to the VGI type.ConclusionsThis represents the first study on the ecology of Cryptococcus spp. associated to trees from northeastern Argentina, and the first report describing Grevillea robusta as a host of members of this fungal genus. Another finding is the isolation of C. neoformans from Tabebuia avellanedae and Peltophorum dubium, both tree species native to northeastern Argentina.     

α-Amylase Expression under Anoxia in Rice Seedlings: An Update

Rice grains can germinate under anoxia, while most other cereals fail to behave similarly. The ability of rice grains to degrade starch, thanks to the successful production of -amylase even in the absence of oxygen is likely one of the factors allowing rice to germinate anaerobically. In this paper we review the most recent results concerning the physiology and molecular biology related to the expression of -amylase genes under anoxia. The current view is that expression of sugar-starvation induces isoforms of -amylase playing a major role during germination under anoxia, while gibberellin induces -amylase predominating under aerobic conditions.     

Leaders in Cell Adhesion: An Interview with Richard Hynes,Pioneer of Cell–Matrix Interactions

Abstract

On a recent visit Richard O Hynes, FRS, HHMI, Daniel K. Ludwig Professor for Cancer Research at the Koch Institute for Integrative Cancer Research, MIT, graciously agreed to be interviewed in person for the first in Cell Communication and Adhesion's series on “Leaders in Cell Adhesion”. In this interview we discussed three things: 1) the early role of family, mentors, and luck on his career path; 2) his major discoveries of fibronectin, integrins and the evolution of extracellular matrix proteins; and 3) his role in, and thoughts on, current science policy. This interview reveals his characteristic calmness and infectious optimism, his spontaneous and down to earth sense of humor, and his great ability to place scientific questions in perspective. The interview, carried out on April 30^th 2013 is reported here verbatim with only minor editing for clarity.     

Dancing with the Diva: Hsp90–Client Interactions

The molecular chaperone Hsp90 is involved in the folding, maturation, and degradation of a large number structurally and sequentially unrelated clients, often connected to serious diseases. Elucidating the principles of how Hsp90 recognizes this large variety of substrates is essential for comprehending the mechanism of this chaperone machinery, as well as it is a prerequisite for the design of client specific drugs targeting Hsp90. Here, we discuss the recent progress in understanding the substrate recognition principles of Hsp90 and its implications for the role of Hsp90 in the lifecycle of proteins. Hsp90 acts downstream of the chaperone Hsp70, which exposes its substrate to a short and highly hydrophobic cleft. The subsequently acting Hsp90 has an extended client-binding interface that enables a large number of low-affinity contacts. Structural studies show interaction modes of Hsp90 with the intrinsically disordered Alzheimer's disease-causing protein Tau, the kinase Cdk4 in a partially unfolded state and the folded ligand-binding domain of a steroid receptor. Comparing the features shared by these different proteins provides a picture of the substrate-binding principles of Hsp90.     

Virus–Receptor Interactions: The Key to Cellular Invasion

Virus–receptor interactions play a key regulatory role in viral host range, tissue tropism, and viral pathogenesis. Viruses utilize elegant strategies to attach to one or multiple receptors, overcome the plasma membrane barrier, enter, and access the necessary host cell machinery. The viral attachment protein can be viewed as the “key” that unlocks host cells by interacting with the “lock”—the receptor—on the cell surface, and these lock-and-key interactions are critical for viruses to successfully invade host cells. Many common themes have emerged in virus–receptor utilization within and across virus families demonstrating that viruses often target particular classes of molecules in order to mediate these events. Common viral receptors include sialylated glycans, cell adhesion molecules such as immunoglobulin superfamily members and integrins, and phosphatidylserine receptors. The redundancy in receptor usage suggests that viruses target particular receptors or “common locks” to take advantage of their cellular function and also suggests evolutionary conservation. Due to the importance of initial virus interactions with host cells in viral pathogenesis and the redundancy in viral receptor usage, exploitation of these strategies would be an attractive target for new antiviral therapeutics.     

Tick–Host–Borrelia Population Interactions: Long-Term Records in Eastern Europe

During 10 spring and summer seasons (1992–2001), the dynamics of the epizootic process in natural foci were studied in taiga forests of the Pre-Ural region, Russia. In these foci, Borrelia garinii, Borrelia afzelii and tick-borne encephalitis (TBE) virus circulate transmitted by their main vector tick, Ixodes persulcatus. Main parameters of the epizootic process were calculated for each season. In three seasons (1993, 1996, and 1999) all parameters characterizing the abundance of unfed nymphs and adult ticks, as well as the prevalence of Borrelia and TBE virus in them, increased sharply and simultaneously. These seasons were preceded by years of population peaks in forest rodents (1992, 1995, and 1998), especially Clethrionomys glareolus voles, the dominant species in the local mammalian fauna. Apparently, the possibility of horizontal transmission of the agents of tick-borne infections sharply increases in such years and this results in the intensification of their dissemination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Trichoderma–Plant–Pathogen Interactions: Advances in Genetics of Biological Control

Trichoderma spp. are widely used in agriculture as biofungicides. Induction of plant defense and mycoparasitism (killing of one fungus by another) are considered to be the most important mechanisms of Trichoderma-mediated biological control. Understanding these mechanisms at the molecular level would help in developing strains with superior biocontrol properties. In this article, we review our current understanding of the genetics of interactions of Trichoderma with plants and plant pathogens.