Characterization of ftsZ Mutations that Render Bacillus subtilis Resistant to MinC

Background

Cell division in Bacillus subtilis occurs precisely at midcell. Positional control of cell division is exerted by two mechanisms: nucleoid occlusion, through Noc, which prevents division through nucleoids, and the Min system, where the combined action of the MinC, D and J proteins prevents formation of the FtsZ ring at cell poles or recently completed division sites.

Methodology/Principal Findings

We used a genetic screen to identify mutations in ftsZ that confer resistance to the lethal overexpression of the MinC/MinD division inhibitor. The FtsZ mutants were purified and found to polymerize to a similar or lesser extent as wild type FtsZ, and all mutants displayed reduced GTP hydrolysis activity indicative of a reduced polymerization turnover. We found that even though the mutations conferred in vivo resistance to MinC/D, the purified FtsZ mutants did not display strong resistance to MinC in vitro.

Conclusions/Significance

Our results show that in B. subtilis, overproduction of MinC can be countered by mutations that alter FtsZ polymerization dynamics. Even though it would be very likely that the FtsZ mutants found depend on other Z-ring stabilizing proteins such as ZapA, FtsA or SepF, we found this not to be the case. This indicates that the cell division process in B. subtilis is extremely robust.     

Frequency and functional activity of Th17, Tc17 and other T-cell subsets in Systemic Lupus Erythematosus

To compare frequency and functional activity of peripheral blood (PB) Th(c)17, Th(c)1 and Treg cells and the amount of type 2 cytokines mRNA we recruited SLE patients in active (n = 15) and inactive disease (n = 19) and healthy age- and gender-matched controls (n = 15). The study of Th(c)17, Th(c)1 and Treg cells was done by flow cytometry and cytokine mRNA by real-time PCR. Compared to NC, SLE patients present an increased proportion of Th(c)17 cells, but with lower amounts of IL-17 per cell and also a decreased frequency of Treg, but with increased production of TGF-β and FoxP3 mRNA. Ιn active compared to inactive SLE, there is a marked decreased in frequency of Th(c)1 cells, an increased production of type 2 cytokines mRNA and a distinct functional profile of Th(c)17 cells. Our findings suggest a functional disequilibrium of T-cell subsets in SLE which may contribute to the inflammatory process and disease pathogenesis.     

Unfolding of cardosin A in organic solvents and detection of intermediaries

In the present study the relationship between conformational stability and enzymatic activity in the presence of organic solvents (OS) was investigated. We have found that cardosin A, the model protease investigated in this work, inactivates through a biphasic mechanism, which is incipient in aqueous buffer and becomes visible in the presence of hydrophilic OS. In fact, in OS this inactivation originates stable intermediaries that were detected in acetonitrile. This biphasic mechanism can be described in two phases: an initial one, where OS induce alterations that affect the active site cleft and global mobility, but with little interference on the global protein conformation, and, a second phase, where there is a global change in protein conformation with concomitant activity loss. It is shown that in the presence of hydrophilic OS there is a larger mobility of the enzyme, revealed by limited proteolysis, probably due to a weakening of hydrophobic interactions within the protein core.     

Resistance to beta-lactam antibiotics in Aeromonas hydrophila isolated from rainbow trout (Oncorhynchus mykiss).

Bacterial infections caused by members of the genus Aeromonas, with a relatively high antibiotic resistance, are among the most common and troublesome diseases of fish raised in ponds with recirculation systems. In this study, carried out at an experimental aquaculture station in northern Portugal, 51 strains identified as belonging to the genus Aeromonas were isolated from 20 rainbow trout (Oncorhynchus mykiss) skin and kidney samples, as well as from raceway water samples. Macro- and microscopic examination of the fish tissues revealed lesions or cellular alterations in skin and kidney that seemed to correlate with the presence of those isolates. The sensitivity of all isolated strains to different groups of beta-lactam antibiotics (penicillins, cephalosporins, monobactams and carbapenems) was evaluated using the disc diffusion method. The highest rates of resistance were to amoxicillin, carbenicillin and ticarcillin. Unexpected resistance to imipenem, an antibiotic of clinical usage, was also detected, which suggests that resistance may have been transferred to the Aeromonas population from the environment.     

Ptychomitrium subcrispatum Thér. & P.de la Varde,an east southern African species excluded from the Cape Verde bryoflora

Abstract

Pictolejeunea levis, a new species of Lejeuneaceae found in N.E. Cuba, is described and illustrated. The species stands out within Pictolejeunea on account of its smooth leaf cells and the presence of ocelli on dorsal and ventral epidermal cells of the stem. Differences between this and the other four known species in the genus are discussed.     

Function of dorsal fins in bamboo shark during steady swimming

To gain insight into the function of the dorsal fins in white-spotted bamboo sharks (Orectolobiformes: Hemiscyillidae) during steady swimming, data on three-dimensional kinematics and electromyographic recordings were collected. Bamboo sharks were induced to swim at 0.5 and 0.75 body lengths per second in a laminar flow tank. Displacement, lag and angles were analyzed from high-speed video images. Onset, offset, duration, duty cycle and asynchrony index were calculated from three muscle implants on each side of each dorsal fin. The dorsal fins were displaced more laterally than the undulating body. In addition, the dorsal tips had larger lateral displacement than the trailing edges. Increased speed was accompanied by an increase in tail beat frequency with constant tail beat amplitude. However, lateral displacement of the fins and duration of muscle bursts remained relatively constant with increased speed. The range of lateral motion was greater for the second dorsal fin (mean 33.3°) than for the first dorsal fin (mean 28.4°). Bending within the fin was greater for the second dorsal fin (mean 43.8°) than for the first dorsal fin (mean 30.8°). Muscle onset and offset among implants on the same side of each dorsal fin was similar. Three-dimensional conformation of the dorsal fins was caused by interactions between muscle activity, material properties, and incident flow. Alternating bilateral activity occurred in both dorsal fins, further supporting the active role of these hydrofoils in thrust production during steady swimming. The dorsal fins in bamboo sharks are capable of thrust production during steady swimming and do not appear to function as stabilizing structures.     

Catalytic dehydration of xylose to furfural: vanadyl pyrophosphate as source of active soluble species

The acid-catalysed, aqueous phase dehydration of xylose (a monosaccharide obtainable from hemicelluloses, e.g., xylan) to furfural was investigated using vanadium phosphates (VPO) as catalysts: the precursors, VOPO₄·2H₂O, VOHPO₄·0.5H₂O and VO(H₂PO₄)₂, and the materials prepared by calcination of these precursors, that is, γ-VOPO₄, (VO)₂P₂O₇ and VO(PO₃)₂, respectively. The VPO precursors were completely soluble in the reaction medium. In contrast, the orthorhombic vanadyl pyrophosphate (VO)₂P₂O₇, prepared by calcination of VOHPO₄·0.5H₂O at 550 °C/2 h, could be recycled by simply separating the solid acid from the reaction mixture by centrifugation, and no drop in catalytic activity and furfural yields was observed in consecutive 4 h-batch runs (ca. 53% furfural yield, at 170 °C). However, detailed catalytic/characterisation studies revealed that the vanadyl pyrophosphate acts as a source of active water-soluble species in this reaction. For a concentration of (VO)₂P₂O₇ as low as 5 mM, the catalytic reaction of xylose (ca. 0.67 M xylose in water, and toluene as solvent for the in situ extraction of furfural) gave ca. 56% furfural yield, at 170 °C/6 h reaction.     

Proinflammatory environment dictates the IL-17-producing capacity of human invariant NKT cells

CD1d-reactive invariant NKT (iNKT) cells have been implicated in a number of experimental models of human pathologies. Given the scope of their immunoregulatory activities mediated through distinct cytokine patterns, it has been proposed that this functional diversity originates from distinct iNKT subpopulations. In this study, we report that human CD161(+) iNKT cells are intrinsically endowed with the capacity to generate IL-17, but require TGF-β, IL-1β, and IL-23 to carry out this potential. IL-17-producing iNKT cells are already present in cord blood but, in contrast to peripheral blood iNKT cells, they cannot generate IFN-γ. These IL-17 producers respond to aryl hydrocarbon receptor stimulation and express IL-23 receptor and retinoic acid-related orphan receptor C, similar to conventional T helper 17 cells, from which they differ by their restricted ability to coproduce IL-22. In conclusion, IL-17 production by human iNKT cells depends on two critical parameters, namely an intrinsic program and a proinflammatory environment.     

Prey handling using whole-body fluid dynamics in batoids

Fluid flow generated by body movements is a foraging tactic that has been exploited by many benthic species. In this study, the kinematics and hydrodynamics of prey handling behavior in little skates, Leucoraja erinacea, and round stingrays, Urobatis halleri, are compared using kinematics and particle image velocimetry. Both species use the body to form a tent to constrain the prey with the pectoral fin edges pressed against the substrate. Stingrays then elevate the head, which increases the volume between the body and the substrate to generate suction, while maintaining pectoral fin contact with the substrate. Meanwhile, the tip of the rostrum is curled upwards to create an opening where fluid is drawn under the body, functionally analogous to suction-feeding fishes. Skates also rotate the rostrum upwards although with the open rostral sides and the smaller fin area weaker fluid flow is generated. However, skates also use a rostral strike behavior in which the rostrum is rapidly rotated downwards pushing fluid towards the substrate to potentially stun or uncover prey. Thus, both species use the anterior portion of the body to direct fluid flow to handle prey albeit in different ways, which may be explained by differences in morphology. Rostral stiffness and pectoral fin insertion onto the rostrum differ between skates and rays and this corresponds to behavioral differences in prey handling resulting in distinct fluid flow patterns. The flexible muscular rostrum and greater fin area of stingrays allow more extensive use of suction to handle prey while the stiff cartilaginous rostrum of skates lacking extensive fin insertion is used as a paddle to strike prey as well as to clear away sand cover.