Gram-Negative Bacterial Lipopolysaccharide Retention by a Positively Charged New-Generation Filter

Removing endotoxins is an important target in the pharmaceutical industry and in clinical practice. A filter introduced into an intravenous line prevents microbiological contamination, but to date no filters have retained bacterial endotoxins. In our study, we assayed a new-generation filter which is able to capture endotoxins from solutions.     

<Emphasis Type="Italic">Fusarium equiseti</Emphasis> LPSC 1166 and its in vitro role in the decay of <Emphasis Type="Italic">Heterostachys ritteriana</Emphasis> leaf litter

The role of microorganisms in litter degradation in arid and semi-arid zones, where soil and water salinization is one of the main factors limiting carbon turnover and decay, remains obscure. Heterostachys ritteriana (Amaranthaceae), a halophyte shrub growing in arid environments such as “Salinas Grandes” (Córdoba, Argentina), appears to be the main source of organic matter in the area. Little is known regarding the microorganisms associated with H. ritteriana, although they are a potential source of enzymes such as cellulolytic ones, which might be important in biotechnological fields such as bioethanol production using ionic liquids. In the present study, by studying the microbiota growing on H. ritteriana leaf litter in “Salinas Grandes,” we isolated the cellulolytic fungus Fusarium equiseti LPSC 1166, which grew and degraded leaf litter under salt stress. The growth of this fungus was a function of the C substrate and the presence of NaCl. Although in vitro the fungus used both soluble and polymeric compounds from H. ritteriana litter and synthesized extracellular β-1,4 endoglucanases, its activity was reduced by 10% NaCl. Based on these results, F. equiseti LPSC 1166 can be described as a halotolerant cellulolytic fungus most probably playing a key role in the decay of H. ritteriana leaf litter in “Salinas Grandes.”     

Aeration requirements ofRhizobium cultures

Summary To obtain a high concentration ofRhizobium in broth cultures, the process conditions should be adjusted to the medium and strain used. Oxygen may be a growth-limiting factor if the micro-organism requirements are not satisfied. In this work the process conditions in shake flasks and stirred fermenters were established, based on the oxygen supply rate, in relation to the cell oxygen demand of the variousRhizobium strains used in inoculant preparations. The strains used wereRhizobium meliloti B-36,R. phaseoli F-10,R. trifolii A-22,Rhizobium spp. LL-22,R-leguminosarum D-91 andR. japonicum 5019. They had maximum oxygen demand rates from 135 to 360 ml O₂/l/h in media containing 10 g of carbon source/l, 4 g of yeast extract/l and mineral salts. When the operations were conducted in Erlenmeyer flasks with a volume liquid/volume flask of 0.150 in a rotary shaker at 250 rev/min and 2.5 cm eccentricity, the oxygen absorption rate was 355 ml O₂/l/h. In mechanically stirred fermenters with a liquid depth/fermenter diameter of 1, with an agitation rate of 250 to 450 rev/min and an air flow rate of 0.5 v/v/min, the bacteria had oxygen absorption rates of between 233 and 661 ml O₂/l/h. These conditions allowed the attainment of 1.2 to 2.4×10¹⁰ viable cells/ml from between 24 and 72 h.

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Resumen Para obtener alta concentración de células deRhizobium en caldos de fermentación deben ajustarse las condiciones de proceso al medio y cepas utilizadas. El oxígeno puede resultar uno de los factores limitante del crecimiento si no satisfacen las necesidades del microorganismo. En el presente trabajo se establecen condiciones de proceso en Erlenmeyers agitados y en fermentadores en base a la velocidad de absorción de oxígeno y relación a la demanda para los medios y las distintas cepas utilizadas en la preparación de inoculantes. Las cepas empleadas,Rhizobium meliloti B-36;R. phaseoli F-10;R. trifolii A-22;Rhizobium spp. LL-22;R. leguminosarum D-91; yR. japonicum 5019, presentaron máximos valores de demanda de oxígeno en el rango de 135 a 360 ml O₂/l/h en medios que contienen 10g/l de fuente de carbono, 4g/l de extracto de levadura y sales minerales. Para las especies indicadas se estableció que operando en agitador rotatorio a 250 r.p.m. y 2,5 cm de excentricidad deben utilizarse Erlenmeyers con una relación de volumen de líquido a volumen de frasco de 0,150 (para estas condiciones la velocidad de absorción de oxígeno es de 355 ml O₂/l/h) mientras que en fermentadores con agitación mecánica y para una relación de altura de líquido a diámetro de tanque igual a uno las condiciones establecidas se encuentran comprendidas en el ámbito de velocidades de agitación de 250 a 450 r.p.m. y caudal de aire de 0,5 v/v/min (estos valores corresponden a velocidades de absorción de oxígeno comprendidas entre 233 a 61 ml O₂/l/h). Las condiciones indicadas permiten obtener concentraciones celulares de 1,2 a 2,4×10¹⁰ cel/ml en tiempos de 24 a 72 horas de proceso.

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Résumé Pour obtenir une haute concentration de cellules deRhizobium dans des milieux de fermentation, il faut ajuster les conditions de processus au milieu et aux souches utilisés. L'oxygène peut être un des facteurs limitants de la croissance du microorganisme si ses besoins ne sont pas assouvis. Dans ce travail, pour les milieux employés, on établit des conditions de processus dans des Erlenmeyers et dans des fermenteurs. Ces conditions se basent sur la vitesse d'absorption d'oxygène et sur la demande cellulaire, de différentes souches deRhizobium, utilisées dans la préparation d'inoculants. Les souches employées sont:Rhizobium meliloti B-36;R. phaseoli F-10;R. trifolii A-22;Rhizobium spp. LL-22;R. leguminosarum D-91 etR. japonicum 5019. Elles ont presenté des valeurs du besoin maxima d'oxygène entre 135 et 360 ml O₂/l/h dans des milieux contenant 10g/l de source de carbone, 4g/l d'extrait de levure et sels minéraux. Pour les espèces indiquées, en opérant dans un agitateur rotatif à 250 tours/minute et 2,5 cm d'excentricité on a établi qu'il faut utiliser des Erlenmeyers dont le rapport volume de milieu liquide/volume de récipient est 0,150 (pour ces conditions, la vitesse d'absorption d'oxygène est 355 ml O₂/l/h); tandis que dans des fermenteurs avec agitation mécanique et pour un rapport hauteur de milieu liquide/diamètre de tank égal à l, les conditions établies se trouvent entre vitesses d'agitation de 250 à 450 tours/minute et un débit d'air de 0,5 litre par volume de milieu et par minute (ces valeurs d'operation correspondent aux vitesses d'absorption d'oxygène de 233 à 661 ml O₂/l/h). Ces conditions permettent d'obtenir des concentrations cellulaires de 1,2 à 2,4×10¹⁰ cellules viables par millilitre apres 24 à 72 heures de processus.

     

A coarse-grained approach to studying the interactions of the antimicrobial peptides aurein 1.2 and maculatin 1.1 with POPG/POPE lipid mixtures

In the present work we investigated the differential interactions of the antimicrobial peptides (AMPs) aurein 1.2 and maculatin 1.1 with a bilayer composed of a mixture of the lipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (POPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE). We carried out molecular dynamics (MD) simulations using a coarse-grained approach within the MARTINI force field. The POPE/POPG mixture was used as a simple model of a bacterial (prokaryotic cell) membrane. The results were compared with our previous findings for structures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), a representative lipid of mammalian cells. We started the simulations of the peptide–lipid system from two different initial conditions: peptides in water and peptides inside the hydrophobic core of the membrane, employing a pre-assembled lipid bilayer in both cases. Our results show similarities and differences regarding the molecular behavior of the peptides in POPE/POPG in comparison to their behavior in a POPC membrane. For instance, aurein 1.2 molecules can adopt similar pore-like structures on both POPG/POPE and POPC membranes, but the peptides are found deeper in the hydrophobic core in the former. Maculatin 1.1 molecules, in turn, achieve very similar structures in both kinds of bilayers: they have a strong tendency to form clusters and induce curvature. Therefore, the results of this study provide insight into the mechanisms of action of these two peptides in membrane leakage, which allows organisms to protect themselves against potentially harmful bacteria.

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Graphical Abstract Aurein pore structure (green) in a lipid bilayer composed by POPE (blue) and POPG (red) mixture. It is possible to see water beads (light blue) inside the pore.

     

Effect of amaranth on the growth of Rhizobium and Bradyrhizobium strains

The growth rate of different strains of Bradyrhizobium and Rhizobium was studied in media containing amaranth seed meal instead of yeast extract. Results obtained in erlenmeyer flasks and stirred fermenters show that both Bradyrhizobium japonicum strains E109, E110, 5019, 587 and Rhizobium melilotistrains B36, B323, B399, Lq₂₂, Lq₄₂, Lq₅₁ and U₃₂₂, grow satisfactorily in amaranth seed meal medium. Cell count obtained for the strains tested was greater than 4 × 10¹⁰ viable cells.ml^–1. Amaranth seed meal (4 g.l^–1) is a suitable component for culture media that can be used instead of yeast extract.     

Olive cultivation in the heart of the Persian Achaemenid Empire: new insights into agricultural practices and environmental changes reflected in a late Holocene pollen record from Lake Parishan,SW Iran

Ancient Persia witnessed one of its most prosperous cultural and socio-economic periods between 550 bc and ad 651, with the successive domination of the Achaemenid, Seleucid, Parthian and Sassanian Empires. During this period agricultural activities increased on the Iranian plateau, as demonstrated by a remarkable arboricultural expansion. However, available data are not very informative about the spatial organization of agricultural practices. The possible links between climate conditions and agricultural activities during this millennium of continuous imperial domination are also unclear, due to the lack of parallel human-independent palaeoclimatic proxies. This study presents a new late Holocene pollen-based vegetation record from Lake Parishan, SW Iran. This record provides invaluable information regarding anthropogenic activities before, during and after the empires and sheds light on (i) spatial patterning in agricultural activities and (ii) possible climate impacts on agro-sylvo-pastoral practices during this period. Results of this study indicate that arboriculture was the most prominent form of agricultural activity in SW Iran especially during the Achaemenid, Seleucid and Parthian periods. Contrary to the information provided by some Greco-Roman written sources, the record from Lake Parishan shows that olive cultivation was practiced during Achaemenid and Seleucid times, when olive cultivation was significant, at least in this basin located close to the capital area of the Achaemenid Empire. In addition, pollen from aquatic vegetation suggests that the period of the latter centuries of the first millennium bc was characterized by a higher lake level, which might have favoured cultural and socio-economic prosperity.     

Growth and nitrogen fixation in soybean (Glycine max (L.) Merr.) as affected by gibberellic acid treatment during reproductive development

Summary Nodulated soybean (Glycine max (L.) Merr.) plants cv. Williams were grown on a N-free medium and sprayed daily, after flowering, with a solution of 0,0.5 or 1.0 mg/l gibberellic acid (GA₃). Relative growth rate, net assimilation rate and mean N₂-fixation rate decreased in control plants from flowering to mid-pod filling. The decline of growth and N₂-fixation was attenuated by GA₃. Lesser decline of growth and N₂-fixation in GA₃-treated plants was linked to enhancement of vegetative growth, to delay of fruit development and to arrest of root decay.

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Resumen Plantas de soja (Glycine max L. Merr.) cv. Williams, noduladas, crecieron en un medio libre de N; se rociaron diariamente, después de la floración, con una solución de 0, 0.5 ó de l mg l^–1 de àcido gibberélico (GA₃). Las tasas de crecimiento relativo, de asimilación neta y de fijación de nitrógeno disminuyeron en las plantas control desde la floración hasta la mitad del periodo de crecimiento de las vainas. La declination del crecimiento y fijación, de N₂ fue atenuada por el ácido gibberélico. Esta menor disminución del crecimiento y de la fijación de N₂ en las plantas tratadas con GA₃, esta asociada a un mayor crecimiento vegetativo, a un retraso en el desarrollo del fruto y a una menor descomposición radicular.

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Résumé Des plants nodulés de soja (Glycine max L. Merr.) ont été cultivés en milieu dépourvu d'azote et aspergés quotidiennement, après la floraison, avec une solution d'acide gibbérellique (GA₃) à des concentrations de 0,0,5 et 1,0 mg/l. Dans le cas des plants témoins, les taux de croissance, d'assimilation nette et de fixation moyenne de l'azote diminuent entre la floraison et la moitié du remplissage des gousses. Chez les plants traités par GA₃, la croissance et la fixation de N₂ diminuent moins, et on constate un accroissement de la croissance végétative, un ralentissement du développement des fruits et un arrêt de la dégénérescence racinaire.

     

Cultivar-Specific Interactions of Soybean with Rhizobium fredii Are Regulated by the Genotype of the Root

Rhizobium fredii USDA257 forms nitrogen-fixing nodules on soybean cultivar Peking, but not on cultivar McCall. This pattern of nodulation persists when McCall and Peking seedlings are cultivated together in plastic growth pouches. Reciprocal grafting experiments confirm that the root genotype, and not that of the shoot, regulates such cultivar specificity. When Peking roots are grafted onto McCall seedlings, the nodulation responses of roots similarly remain unaffected. Transposon-mutant 257DH4, which is derived from USDA257, can form nitrogen-fixing nodules on McCall. Such nodulation is blocked by the presence of USDA257 in the inoculum. Grafting experiments indicate that blocking is not due to a translocatable inhibitor produced by McCall roots or triggered by their interaction with USDA257. Thus, neither freely diffusible nor graft-transmissible substances are involved in cultivar-specific interactions of soybean with R. fredii and its derivatives.