Episodic Rainfall Influences the Distribution and Abundance of the Regular Sea Urchin Lytechinus variegatus in Saint Andrew Bay, Northern Gulf of Mexico

The distribution and abundance of Lytechinus variegatus (Lamarck) were determined at three shallow-water stations in Saint Andrew Bay, FL, in the northern Gulf of Mexico. Populations were monitored at 4-mo intervals from Aug. 1997 to Aug. 1999 along 2- X 10-m transects, with four transects at each station. In Aug. 1997 individuals ranged in size from 15- to 63-mm diameter (mean = 38 mm; density= 1.4 individuals (ind.) m-2) at Station 1 (Stations 2 and 3 were not sampled on that date). By Oct. 1997 individuals at Station 1 ranged in size from 26 to 62 mm (mean = 48 mm; density = 0.6 ind. m-2), suggesting the growth of individuals within the population. At Station 2, individuals ranged between 50 and 70 mm (mean = 59 mm; densities = 1.0 ind. m-2) and at Station 3 between 30 and 79 mm (mean= 51 mm; densities = 1.4 ind, m-2) in Oct. 1997, indicating a population with no recent recruits. A mass mortality event was observed in April 1998 and was attributed to reduced salinities resulting from above-average rainfall in the previous month. Sea urchins were absent at Stations 1 and 2, whereas at Station 3 postdisturbance recruits were smaller (mean = 28 mm) and densities lower. Sea urchin tests were also observed at beach stations proximate to Stations 1 and 2. By July 1998 the populations had partially recovered at Stations 2 and 3 (densities = 0.6 and 1.1 ind. m-2, respectively), but test diameters were small at both stations. Test diameters had increased in Dec. 1998 at Station 3 when compared with those of July, but individuals at Station 2 showed overall smaller test diameters (mean = 28 mm), and densities had decreased again, presumably after another mass mortality caused by another major rainfall in Sep. In April 1999 test diameters had decreased further at Stations 2 and 3, indicating emigration or death of larger animals. We suggest that the shallow-water Saint Andrew Bay population of L. variegatus is reduced for several years at a time by episodic heavy rainfalls. This observation emphasizes the importance of density-independent processes controlling the distribution and abundance of marine organisms

In vitro and in vivo evaluation of synergism between anti-tubercular spectinamides and non-classical tuberculosis antibiotics

Spectinamides are new semi-synthetic spectinomycin derivatives with potent anti-tubercular activity. The reported synergism of the precursor spectinomycin with other antibiotics prompted us to examine whether spectinamides sensitize M. tuberculosis to other antibiotics not traditionally used in the treatment of tuberculosis to potentially expand therapeutic options for MDR/XDR Tuberculosis. Whole cell synergy checkerboard screens were performed using the laboratory strain M. tuberculosis H37Rv, lead spectinamide 1599, and a broad panel of 27 antibiotics. In vitro, 1599 synergized with 11 drugs from 6 antibiotic classes. The observed synergy was tested against clinical isolates confirming synergy with Clarithromycin, Doxycycline and Clindamycin, combinations of which were taken forward for in vivo efficacy determination. Co-administration of 1599 and clarithromycin provided additional bacterial killing in a mouse model of acute tuberculosis infection, but not in a chronic infection model. Further studies indicated that mismatched drug exposure profiles likely permitted induction of phenotypic clarithromycin resistance and subsequent loss of synergism. These studies highlight the importance of validating in vitro synergism and the challenge of matching drug exposures to obtain a synergistic outcome in vivo. Results from this study indicate that a 1599 clarithromycin combination is potentially viable, providing the drug exposures can be carefully monitored

Iron can be microbially extracted from Lunar and Martian regolith simulants and 3D printed into tough structural materials

In-situ resource utilization (ISRU) is increasingly acknowledged as an essential requirement for the construction of sustainable extra-terrestrial colonies. Even with decreasing launch costs, the ultimate goal of establishing colonies must be the usage of resources found at the destination of interest. Typical approaches towards ISRU are often constrained by the mass and energy requirements of transporting processing machineries, such as rovers and massive reactors, and the vast amount of consumables needed. Application of self-reproducing bacteria for the extraction of resources is a promising approach to reduce these pitfalls. In this work, the bacterium Shewanella oneidensis was used to reduce three different types of Lunar and Martian regolith simulants, allowing for the magnetic extraction of iron-rich materials. The combination of bacterial treatment and magnetic extraction resulted in a 5.8-times higher quantity of iron and 43.6% higher iron concentration compared to solely magnetic extraction. The materials were 3D printed into cylinders and the mechanical properties were tested, resulting in a 400% improvement in compressive strength in the bacterially treated samples. This work demonstrates a proof of concept for the on-demand production of construction and replacement parts in space exploration

Spectinamides: a new class of semisynthetic antituberculosis agents that overcome native drug efflux

Although the classical antibiotic spectinomycin is a potent bacterial protein synthesis inhibitor, poor antimycobacterial activity limits its clinical application for treating tuberculosis. Using structure-based design, we generated a new semisynthetic series of spectinomycin analogs with selective ribosomal inhibition and excellent narrow-spectrum antitubercular activity. In multiple murine infection models, these spectinamides were well tolerated, significantly reduced lung mycobacterial burden and increased survival. In vitro studies demonstrated a lack of cross resistance with existing tuberculosis therapeutics, activity against multidrug-resistant (MDR) and extensively drug-resistant tuberculosis and an excellent pharmacological profile. Key to their potent antitubercular properties was their structural modification to evade the Rv1258c efflux pump, which is upregulated in MDR strains and is implicated in macrophage-induced drug tolerance. The antitubercular efficacy of spectinamides demonstrates that synthetic modifications to classical antibiotics can overcome the challenge of intrinsic efflux pump-mediated resistance and expands opportunities for target-based tuberculosis drug discovery