HmuS and HmuQ of <Emphasis Type="Italic">Ensifer</Emphasis>/<Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis> degrade heme in vitro and participate in heme metabolism in vivo

Ensifer meliloti is a nitrogen-fixing symbiont of the alfalfa legume able to use heme as an iron source. The transport mechanism involved in heme acquisition in E. meliloti has been identified and characterized, but the fate of heme once inside the cell is not known. In silico analysis of E. meliloti 1021 genome revealed no canonical heme oxygenases although two genes encoding putative heme degrading enzymes, smc01518 and hmuS, were identified. SMc01518 is similar to HmuQ of Bradyrhizobium japonicum, which is weakly homologous to the Staphylococcus aureus IsdG heme-degrading monooxygenase, whereas HmuS is homolog to Pseudomonas aeruginosa PhuS, a protein reported as a heme chaperone and as a heme degrading enzyme. Recombinant HmuQ and HmuS were able to bind hemin with a 1:1 stoichiometry and displayed a K_d value of 5 and 4 µM, respectively. HmuS degrades heme in vitro to the biliverdin isomers IX-β and IX-δ in an equimolar ratio. The HmuQ recombinant protein degrades heme to biliverdin IX-δ only. Additionally, in this work we demonstrate that humS and hmuQ gene expression is regulated by iron and heme in a RirA dependent manner and that both proteins are involved in heme metabolism in E. meliloti in vivo.     

Patterns of pyrite oxidation by different microorganisms

The bacterial-chemical oxidation of natural pyrites with different physical, chemical, and electrophysical characteristics by bacteria Acidithiobacillus ferrooxidans, Sulfobacillus thermotolerans, and the archaeon Ferroplasma acidiphilum were studied. The electrophysical characteristics of three natural pyrites differed in the K _thermoEMF value (pyrites 3, 4, hole conduction (p-type conductivity); pyrite 5, mixed type conductivity (n-p)) and in the logarithm of electric resistance. Chemical oxidation of pyrites 3 and 5 resulted in no changes of K _thermoEMF. When pyrite 4 was oxidized chemically, the K _thermoEMF values remained in the same range as in the initial sample, but the ratio of grains with different K _thermoEMF values in the sample was changed: the number of grains with a higher K _thermoEMF value increased. The same changes were also observed in the course of bacterio-chemical oxidation of pyrite 4. Of the three pyrites studied, an increase in the logarithm of resistance was observed only for chemical oxidation of pyrite 4 at 28°C. At higher experimental temperatures, the logarithm of resistance increased accordingly; more active bacterial-chemical oxidation resulted in a more pronounced increase in the logarithm of resistance than chemical oxidation. On bacterial-chemical oxidation of pyrites 3 and 5 by A. ferrooxidans and S. thermotolerans strains, iron was leached more actively than sulfur. Preferred bacterial-chemical oxidation of certain fractions from the pyrite samples was shown, namely of the pyrite 3 fraction with higher K _thermoEMF values by the F. acidiphilum strain and of a fraction from the pyrite 5 sample with medium K _thermoEMF values by the A. ferrooxidans and S. thermotolerans strains. The comparative assessment of bacterial-chemical pyrite oxidation by three types of microorganisms showed the direction of changes in the K _thermoEMF values to be the same in the case of bacteria Acidithiobacillus ferrooxidans and Sulfobacillus thermotolerans and different in the case of the archaeon Ferroplasma acidiphilum.     

Changes in the carbohydrate and hormonal status in <Emphasis Type="Italic">Tulipa bifloriformis</Emphasis> bulbs forced into bloom in a greenhouse and in the open ground

Time-course of ABA, cytokinins, monosaccharides (MS), and water-soluble polysaccharides (WSP) contents were followed during cold dormancy period in the bulbs of tulip (Tulipa bifloriformis Vved.) that stayed over winter in the open ground or were cold-forced into bloom in a greenhouse. In both cases, the level of monosaccharides and water-soluble polysaccharides in the storage scale tissues increased, whereas the MS/WSP ratio in the bulbs planted in the open remained essentially the same and in case of forcing treatment decreased almost fivefold. In the apical bud tissues, the level of monosaccharides also rose in both cases, but the MS/WSP ratio in the open was greater throughout the whole experiment. The level of cytokinins in the apical bud tissues in the open was higher than in the forcing case, although the changes in their total content were identical following both treatments. Following the forcing treatment, the contents of free and bound ABA in the apical bud tissues increased reaching their peaks by the end of cold period. In the open, there were two peaks of free ABA: in October (when early frosts occurred) and in March (at the end of the wintering period). The winter forcing treatment resulted in rapid depletion of energy and plastic resources in T. bifloriformis and the death of 20% of embryonic flower buds (in the open, all flower buds survived). Nevertheless, plant adaptation potential ensured the development of generative shoots with 4–5 normal flowers, which makes it possible to use this species of multiflorous tulip for winter forcing in a greenhouse.     

Predictive systems ecology

Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of predictive systems ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practised and we summarize a range of terrestrial and marine examples. Significant challenges remain but we suggest that ecology would benefit both as a scientific discipline and increase its impact in society if it were to embrace the need to become more predictive.     

The Ketogenic Diet and Hyperbaric Oxygen Therapy Prolong Survival in Mice with Systemic Metastatic Cancer

Introduction

Abnormal cancer metabolism creates a glycolytic-dependency which can be exploited by lowering glucose availability to the tumor. The ketogenic diet (KD) is a low carbohydrate, high fat diet which decreases blood glucose and elevates blood ketones and has been shown to slow cancer progression in animals and humans. Abnormal tumor vasculature creates hypoxic pockets which promote cancer progression and further increase the glycolytic-dependency of cancers. Hyperbaric oxygen therapy (HBO₂T) saturates tumors with oxygen, reversing the cancer promoting effects of tumor hypoxia. Since these non-toxic therapies exploit overlapping metabolic deficiencies of cancer, we tested their combined effects on cancer progression in a natural model of metastatic disease.

Methods

We used the firefly luciferase-tagged VM-M3 mouse model of metastatic cancer to compare tumor progression and survival in mice fed standard or KD ad libitum with or without HBO₂T (2.5 ATM absolute, 90 min, 3x/week). Tumor growth was monitored by in vivo bioluminescent imaging.

Results

KD alone significantly decreased blood glucose, slowed tumor growth, and increased mean survival time by 56.7% in mice with systemic metastatic cancer. While HBO₂T alone did not influence cancer progression, combining the KD with HBO₂T elicited a significant decrease in blood glucose, tumor growth rate, and 77.9% increase in mean survival time compared to controls.

Conclusions

KD and HBO₂T produce significant anti-cancer effects when combined in a natural model of systemic metastatic cancer. Our evidence suggests that these therapies should be further investigated as potential non-toxic treatments or adjuvant therapies to standard care for patients with systemic metastatic disease.     

Stress-protective and cross action of the extracellular reactivating factor of the microorganisms of the domains Bacteria, Archaea, and Eukaryota

Cross protection of members of the domains Bacteria, Archaea, and lower Eukaryota from stress factors due to the action of extracellular low-molecular metabolites with adaptogenic functions was shown. The adaptogen produced by Luteococcus japonicus subsp. casei and described previously as a reactivating factor (RF) was shown to protect the yeasts Saccharomyces cerevisiae, archaea Haloarcula marismorti, and the cells of higher eukaryotes (HeLa) against weak stressor impacts. Production of an archaeal extracellular metabolite with a weak adaptogenic effect of the producer cells and capable of a threefold increase in survival of heat-inactivated yeast cells was discovered. Our results confirm the similarity of the compensatory adaptive reactions in prokaryotes (bacteria and archaea) and eukaryotes.     

Prediction of alterations in cardiac functions (ECG data) in the course of the permanent monitoring of cosmonauts starting from selection until return to earth after short space flights

Analysis of alterations in the cardiac activity on the basis of electrocardiographic (ECG) findings in 29 cosmonauts of flight and ground professions aged from 29 to 61 years after 34 short (8–30 days) space flights (SFs) between 1982 and 2006 has been carried out. The ECG data at the stage of clinical selection, clinical-physiological examination (CPE) before a SF, at the stage of the launch of a spacecraft (SC) into orbit and its landing on Earth and at the stage of postflight CPE have been analyzed. The analysis of cardiac activity parameters on the basis of ECG data at different stages of observations has led to the identification of three groups of cosmonauts. There were no significant changes or negative tendencies in the alteration of ECG data in the first group (55.2% of the total number of cosmonauts) during the observation period from selection to the end of the SF. The changes that later became more pronounced during the landing on Earth and were retained during postflight CPE have been found in the second group of cosmonauts (in 34.5% cases) at the time of selection and preflight CPE. Considerable disturbances in cardiac activity that are dangerous for human health have been found in ECGs in the third group (10.3%) during the descent from orbit. The data from the study are the first step in the investigation of possible medical risks for the development and improvement of requirements for the medical selection of crews and the admission of subjects with partial health insufficiency on SFs.     

Characteristics of store-operated calcium channels activated by depletion of the endoplasmic reticulum ryanodine-sensitive calcium stores in rat dorsal root ganglion neurons

In neurons of the rat dorsal root ganglia (DRG), using a patch-clamp technique in the whole-cell configuration, we studied the characteristics of calcium channels activated by depletion of the ryanodine-sensitive calcium stores of the endoplasmic reticulum. Current-voltage (I-V) relationships of these store-operated calcium channels were obtained by subtraction of the integral I-V characteristics after application of caffeine from the integral I-V characteristics of calcium channels in the control. Currents through store-operated calcium channels could be induced by application of a series of hyperpolarization current pulses to the cell under conditions of replacement of a calcium-free solution containing caffeine by a caffeine-free solution containing 2 mM Ca²⁺. In this case, the following two main conditions were abserved: Voltage-operated calcium channels were inactivated, while a gradient of the electrochemical potential for calcium ions was increased, which made easier passing of these currents through store-operated calcium channels. Therefore, we found that in DRG neurons, despite the presence of great numbers of both voltage-operated and receptor-dependent calcium channels, one more mechanism underlying the entry of calcium through store-operated channels does exist. Neirofiziologiya/Neurophysiology, Vol. 39, No. 3, pp. 195–200, May–June, 2007.