Iron requirement and siderophore production in Rhizobium ciceri during growth on an iron-deficient medium

Under conditions of iron limitation many rhizospheric bacteria produce siderophores, ferric iron-specific ligands, which may enhance plant growth by increasing the availability of iron near the roots. Thirty-five strains of Rhizobium ciceri, specific to chickpea (Cicer arietinum L.), were screened for their ability to grow on iron-deficient medium and to produce siderophores. Maximal growth of all strains previously depleted in iron was obtained in medium containing 5 to 10 m of ferric iron. When iron limitation was achieved by the addition of 2,2-bipyridyl or EDDHA [ethylene diamine di(o-hydroxyphenyl) acetic acid] to the medium, only two strains were able to scavenge iron and grow. Siderophore production by these two strains was detected by the Chrome Azurol S assay (CAS), a universal test for siderophores. No hydroxamate-type siderophores were detected in the supernatants of Rhizobium ciceri cultures. However, some strains secreted salicylic acid and 2,3-dihydroxybenzoic acid as phenolate-type siderophores. Addition of ferric iron to the culture medium increased growth yield significantly but depressed the production of siderophores. Although these compounds are produced in response to iron deficiency, nutritive components of the culture medium significantly affected their production. It seems that CuII, MoVI and MnII ions bound competitively with iron to siderophores, resulting in a 34 to 100% increase in production.     

Choline acetyltransferase activity of spinal cord cell cultures increased by co-culture with muscle and by muscle-conditioned medium

Activity of the enzyme choline acetyltransferase (CAT), which mediates the synthesis of the neurotransmitter, acetylcholine, was increased up to 20- fold in spinal cord (SC) cells grown in culture with muscle cells for 2 wk. This increase was directly related to the duration of co-culture as well as to the cell density of both the SC and muscle involved and was not affected by the presence of the acetylcholine receptor blocking agent, α-bungarotoxin. Glutamic acid decarboxylase (GAD) activity was often markedly decreased in SC-muscle cultures while the activities of acetylcholinesterase and several other enzymes were little changed. Increased CAT activity was also observed when SC cultures were maintained in medium which had been conditioned by muscle cells or by undifferentiated cells from embryonic muscle. Muscle-conditioned medium (CM) did not affect the activities of SC cell GAD or acetylcholinesterase. Dilution or concentration of the CM directly affected its ability to increase SC CAT activity , as did the duration and timing of exposure of the SC cells to the CM. The medium could be conditioned by muscle cells in the presence or absence of serum, and remained effective after dialysis or heating to 58 degrees C. Membrane filtration data were consistent with the conclusion that the active material(s) in CM had a molecular weight in excess of 50,000 daltons. We conclude that large molecular weight material that is released by muscle cells is capable of producing a specific increase in CAT activity of SC cells.     

Mosquitoes and transmission of malaria parasites – not just vectors

The regional malaria epidemics of the early 1900s provided the basis for much of our current understanding of malaria epidemiology. Colonel Gill, an eminent malariologist of that time, suggested that the explosive nature of the regional epidemics was due to a sudden increased infectiousness of the adult population. His pertinent observations underlying this suggestion have, however, gone unheeded. Here, the literature on Plasmodium seasonal behaviour is reviewed and three historical data sets, concerning seasonal transmission of Plasmodium falciparum, are examined. It is proposed that the dramatic seasonal increase in the density of uninfected mosquito bites results in an increased infectiousness of the human reservoir of infection and, therefore, plays a key role in "kick-starting" malaria parasite transmission.     

Hereditary Disorders in Circassians of the Karachay-Cherkess Republic

The paper aims to review the diversity of monogenic hereditary disorders (MHD) in the Circassians of the Karachay-Cherkess Republic (KCR). In total, 50817 Circassians were investigated. The populations of eight districts (Ust-Dzhegutinsky, Karachayevsky, Malokarachayevsky, Prikubansky, Khabezsky, Abazinsky, Nogaysky, and Adyge-Khablsky) and of the city of Cherkessk were studied. Two hundred fifty patients from 167 families were registered. The prevalence of MHD in Circassians happens to be 1: 214. The nosological spectrum of MHD in Circassians includes 70 disorders: 34 with autosomal dominant, 25 with autosomal recessive, and 11 with X-linked inheritance patterns. Confirmatory DNA diagnostics was performed in 56 patients. Accumulation of particular diseases in the Circassian population was revealed in comparison with the previously surveyed ethnic groups/populations of Russia. The cluster analysis was performed on the basis of the prevalence of AD and AR disorders and determined the genogeographic position of the Circassians among eight ethnic groups of Russia (13 populations in total). The total size of the surveyed populations was over 3.5 million people: six Russian regions, Tatars of the Tatarstan, Bashkirs of the Bashkortostan, Chuvashs of the Chuvash Republic, Maris of the Mari El Republic, Udmurts of the Udmurt Republic, Adygeans of the Republic of Adygea, and Circassians of the Karachay-Cherkess Republic. The general pattern for AD and AR diseases was similar: six Russian populations group within a single cluster, being remote from people of the Volga-Ural region and the North Caucasus (Adyghe: Adygeans and Circassians).     

Medical Genetic Study of Hereditary Diseases in Abazins of the Karachay-Cherkess Republic

This paper estimates the load and nosological spectrum of monogenic hereditary diseases (HDs) in Abazins of the Karachay-Cherkess Republic (KChR), identified in Cherkessk and ten districts, Abazinsky, Ust-Dzhegutinsky, Malokarachaevsky, Karachaevsky, Prikubansky, Khabezsky, Nogaysky, Adyge-Khablsky, Urupsky, and Zelenchuksky. The number of the investigated population was 387231 individuals (including 33264 Abazins). We detected 153 patients from 105 families with 45 nosological forms of HDs: 83 patients from 50 families with 23 AD diseases, 47 patients from 42 families with 15 AR diseases, and 23 patients from 13 families with 7 X-linked diseases. The total load of HDs in Abazins was 1: 218 individuals (in the rural population 1: 162, in the urban population 1: 305). Frequent and rare nosological forms of HDs and the accumulation of certain diseases in Abazins in comparison with the previously surveyed populations of Russia were determined. On the basis of the prevalence of AD and AR hereditary diseases, a principal component analysis was carried out, which determined the genogeographical position of Abazins among nine ethnic groups (13 populations) of Russian Federation: six Russian regions, Bashkirs of the Bashkortostan, Tatars of the Tatarstan, Chuvashes of the Chuvashia, Maris of the Mari El, Udmurts of the Udmurtia, Adygeans of the Adygea, and Circassians and Abazins of the KChR.     

<Emphasis Type="Italic">Dunaliella salina</Emphasis> exopolysaccharides: a promising biostimulant for salt stress tolerance in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis>)

Microalgal exopolysaccharides represent a potential sustainable alternative for the enhancement and protection of agricultural crops including management of both biotic and abiotic stress. In the present study, we investigated the potential of Dunaliella salina exopolysaccharides (PS) to attenuate the effect of salt stress on growth of Solanum lycopersicum, which was grown under different salinity levels (3 and 6 g L^?1 NaCl). The effects of PS treatment on plant growth, osmoprotectant molecules, protein content, and antioxidant enzymes activities of tomato plants under salt stress were analyzed. A metabolomics study showed that the exopolysaccharides released by D. salina contained sulfated moiety along with carbohydrates and uronic acids. The application of sulfated exopolysaccharides on tomato plants alleviated the salt stress and mitigated the decrease in length and dry weight of the plant’s shoot and root systems, as well as that of potassium (K⁺), and K⁺/Na⁺ ratio. Furthermore, the increase in proline, phenolic compounds, Na⁺, and antioxidant enzymes (CAT, POD, SOD) activities caused by salt stress were attenuated after the exopolysaccharide treatment. GC-MS metabolomics analysis showed that PS treatment allowed the activation and/or inhibition of various metabolic pathways involved in the plant’s tolerance to stress such as jasmonic acid-dependent pathways. This study shows the potential of microalgal exopolysaccharides for enhancing tomato tolerance to salt stress and highlights the possibility of their use as plant growth biostimulants under harsh environmental conditions.     

Plant Size-dependent Escaping Behavior of Gregarious Nymphs of the Desert Locust, Schistocerca gregaria

The present study involves the tracking of marching bands of more than 300,000 gregarious nymphs of the desert locust, Schistocerca gregaria, to examine shelter plant preference and how species and size of shelter plants and nymphal group sizes jointly influence the escaping behavior of 4th- and 5th-instar gregarious nymphs. Field observations are conducted during daytime and night-time in the Sahara Desert in Mauritania. Three dominant plant species have been identified at the survey site: Hyoscyamus muticus, Panicum turgidum, and Nucularia perrini. The smallest mean plant size among the three plant species is H. muticus. Gregarious nymphs perch on all the three plant species irrespective of time, and form various sizes of groups ranging from <10 to >10,000 nymphs. Groups of gregarious locusts perching on the plants show either escaping or sheltering behavior in response to an approaching observer. Percentages of nymphal groups showing escaping behavior for H. muticus, P. turgidum and N. perrini are 96.4, 47.6 and 19.5 %, respectively. Defensive behavior is not affected by nymphal group size but by species and size of shelter plants. Nymphal groups tend to show escaping behavior when their perching plants are relatively small. No groups escape from their perching plants during night. These results might indicate that gregarious nymphs do not have a strong shelter plant preference and change their defensive behavior depending on species and size of sheltering plants and light conditions.