Evolution of culture broth rheological properties during propagation of the entomopathogenic nematode Steinernema carpocapsae,in submerged monoxenic culture

This article presents the evolution of culture broth rheological properties during monoxenic cultures of Steinernema carpocapsae in cylindrical bottles agitated orbitally. Rheological properties were evaluated in simple-shear flow conditions and were well-modeled by the Ostwald-de Waele model. Rheological properties varied from slightly dilatant, n = 1.2 (-), to moderately pseudoplastic flow behavior, n = 0.6 (-). Nematode concentrations increased from 750 +/- 190 to 130 900 +/- 6900 nematodes/mL, and the apparent viscosity (eta(a)) evolved from 4.5 +/- 0.7 to 46.6 +/- 3.2 mPa.s during the fermentations. Rheological behavior did not appear to be strongly influenced by nematode number and/or its stage of development; however, the release of substances from the decomposition of nematode cadavers appeared to be of great importance. Among the different developmental stages of the nematodes, only juveniles of the first stage (J1) were highly susceptible to the shearing conditions tested (shear stress, tau(r)()(theta), from 0.9 to 3.5 Pa during periods of 80-100 min), resulting in the viability loss of 85% of J1 nematodes.     

Antibiotic-producing Micrococcales govern the microbiome that inhabits the fur of two- and three-toed sloths

Sloths have a dense coat on which insects, algae and fungi coexist in a symbiotic relationship. This complex ecosystem requires different levels of controls; however, most of these mechanisms remain unknown. We investigated the bacterial communities inhabiting the hair of two- (Choloepus Hoffmanni) and three-toed (Bradypus variegatus) sloths and evaluated their potential for producing antibiotic molecules capable of exerting control over the hair microbiota. The analysis of 16S rRNA amplicon sequence variants revealed that the communities in both host species are dominated by Actinobacteriota and Firmicutes. The most abundant genera were Brevibacterium, Kocuria/Rothia, Staphylococcus, Rubrobacter, Nesterenkonia and Janibacter. Furthermore, we isolated nine strains of Brevibacterium and Rothia capable of producing substances that inhibited the growth of common mammalian pathogens. The analysis of the biosynthetic gene clusters of these nine isolates suggests that the pathogen-inhibitory activity could be mediated by the presence of siderophores, terpenes, beta-lactones, Type III polyketide synthases, ribosomally synthesized and post-translationally modified peptides, non-alpha poly-amino acids like e-Polylysine, ectoine or non-ribosomal peptides. Our data suggest that Micrococcales that inhabit sloth hair could have a role in controlling microbial populations in that habitat, improving our understanding of this highly complex ecosystem.     

Thermoplasmatales and sulfur-oxidizing bacteria dominate the microbial community at the surface water of a CO2-rich hydrothermal spring located in Tenorio Volcano National Park,Costa Rica

Extremophiles - Here we report the chemical and microbial characterization of the surface water of a CO2-rich hydrothermal vent known in Costa Rica as Borbollones, located at Tenorio Volcano...     

Anti-angiogenic effects of homocysteine on cultured endothelial cells

High levels of homocysteine induce a sustained injury on arterial endothelial cells which accelerates the development of thrombosis and atherosclerosis. Some of the described effects of homocysteine on endothelial cells are features shared with an anti-angiogenic response. Therefore, we studied the effects of homocysteine on key steps of angiogenesis using bovine aorta endothelial cells as a model. Homocysteine decreased proliferation and induced differentiation. Furthermore, 5 mM homocysteine produced strong inhibitions of matrix metalloproteinase-2 and urokinase, two proteolytic activities that play a key role in extracellular matrix re-modeling, and decreased migration and invasion, other two key steps of angiogenesis. This study demonstrates that homocysteine can inhibit several steps of the angiogenic process.     

Photosynthesis can be enhanced by lateral CO2 diffusion inside leaves over distances of several millimeters

This study examines the extent to which lateral gas diffusion can influence intercellular CO(2) concentrations (c(i)) and thus photosynthesis in leaf areas with closed stomata. Leaves were partly greased to close stomata artificially, and effects of laterally diffusing CO(2) into the greased areas were studied by gas-exchange measurement and chlorophyll fluorescence imaging. Effective quantum yields (Delta F/F(m)') across the greased areas were analysed with an image-processing tool and transposed into c(i) profiles, and lateral CO(2) diffusion coefficients (D(C'lat)), directly proportional to lateral conductivities (), were estimated using a one-dimensional (1D) diffusion model. Effective CO(2) diffusion distances in Vicia faba (homobaric), Commelina vulgaris (homobaric) and Phaseolus vulgaris (heterobaric) leaves clearly differed, and were dependent on D(C'lat), light intensity, [CO(2)], and [O(2)]: largest distances were approx. 7.0 mm for homobaric leaves (with high D(C'lat)) and approx. 1.9 mm for heterobaric leaves (low D(C'lat)). Modeled lateral CO(2) fluxes indicate large support of photosynthesis over submillimeter distances for leaves with low D(C'lat), whereas in leaves with large D(C'lat), photosynthesis can be stimulated over distances of several millimeters. For the plant species investigated, the surplus CO(2) assimilation rates of the greased leaf areas (A(gr)) differed clearly, depending on lateral conductivities of the respective leaves.     

Submerged monoxenic culture of the entomopathogenic nematode, <Emphasis Type=Italic>Steinernema carpocapsae</Emphasis> CABA01, in a mechanically agitated bioreactor: Evolution of the hydrodynamic and mass transfer conditions

This study is the first to describe the evolution of both hydrodynamic and oxygen transfer conditions during the submerged culture of the entomopathogenic nematode, Steinernema carpocapsae CABA01 (an indigenous strain isolated within the State of Hidalgo, Mexico), and its symbiotic bacterium, Xenorhabdus nematophila, using an internal-loop mechanically agitated bioreactor of 4.5 L of liquid volume. Concentrations up to 217,306 viable nematodes per mL, with 94% in infective juvenile (IJ) stage (i.e., 204,444 IJ/mL), were achieved in 16 days of bioprocess. The Reynolds number (Re) was used as an index of the actual hydrodynamic conditions, and it varied within the interval 5,150 < Re (dimensionless) < 9,440, involving apparent culture broth viscosity changes from 3 to 5.4 mPa s during the processing. The aeration efficiency was expressed on the basis of the volumetric oxygen transfer coefficient, k _L a, which varied within the range 0.026 to 0.170 s⁻¹.     

Spatio-temporal quantification of differential growth processes in root growth zones based on a novel combination of image sequence processing and refined concepts describing curvature production

Differential growth processes in root and shoot growth zones are governed by the transport kinetics of auxin and other plant hormones. While gene expression and protein localization of hormone transport facilitators are currently being unraveled using state-of-the-art techniques of live cell imaging, the quantitative analysis of growth reactions is lagging behind because of a lack of suitable methods. A noninvasive technique, based on digital image sequence processing, for visualizing and quantifying highly resolved spatio-temporal root growth processes was applied in the model plant Arabidopsis thaliana and was adapted to provide precise information on differential curvature production activity within the root growth zone. Comparison of root gravitropic curvature kinetics in wild-type and mutant plants altered in a facilitator for auxin translocation allowed the determination of differences in the location and in the temporal response of curvature along the growth zone between the investigated plant lines. The findings of the quantitative growth analysis performed here confirm the proposed action of the investigated transport facilitator. The procedure developed here for the investigation of differential growth processes is a valuable tool for characterizing the phenomenology of a wide range of shoot and root growth movements and hence facilitates elucidation of their molecular characterization.     

Increase of the spontaneous mutation rate in a long-term experiment with Drosophila melanogaster

In a previous experiment, the effect of 255 generations of mutation accumulation (MA) on the second chromosome viability of Drosophila melanogaster was studied using 200 full-sib MA1 lines and a large C1 control, both derived from a genetically homogeneous base population. At generation 265, one of those MA1 lines was expanded to start 150 new full-sib MA2 lines and a new C2 large control. After 46 generations, the rate of decline in mean viability in MA2 was approximately 2.5 times that estimated in MA1, while the average degree of dominance of mutations was small and nonsignificant by generation 40 and moderate by generation 80. In parallel, the inbreeding depression rate for viability and the amount of additive variance for two bristle traits in C2 were 2-3 times larger than those in C1. The results are consistent with a mutation rate in the line from which MA2 and C2 were derived about 2.5 times larger than that in MA1. The mean viability of C2 remained roughly similar to that of C1, but the rate of MA2 line extinction increased progressively, leading to mutational collapse, which can be ascribed to accelerated mutation and/or synergy after important deleterious accumulation.