Involvement of etfA gene during CaCO3 precipitation in Bacillus subtilis biofilm

The eftA gene in Bacillus subtilis has been suggested to be involved in the oxidation/reduction reactions during fatty acid metabolism. Interestingly etfA deletion in B. subtilis results in impairment in CaCO3 precipitation on the biofilm. Comparisons between the wild type B. subtilis 168 and its etfA mutant during in vitro CaCO3 crystal precipitation (calcite) revealed changes in phospholipids membrane composition with accumulation of up to 10% of anteiso-C17:0 and 11% iso-C17:0 long fatty acids. Ca2+ nucleation sites such as dipicolinic acid and teichoic acids seem to contribute to the CaCO3 precipitation. etfA mutant strain showed up to 40% less dipicolinic acid accumulation compared with B. subtilis 168, while a B. subtilis mutant impaired in teichoic acids synthesis was unable to precipitate CaCO3. In addition, B. subtilis etfA mutant exhibited acidity production leading to atypical flagella formation and inducing extensive lateral growth on the biofilm when grown on 1.4% agar. From the ecological point of view, this study shows a number of physiological aspects that are involved in CaCO3 organomineralization on biofilms

Factors affecting formation of large calcite crystals (≥1mm) in Bacillus subtilis 168 biofilm

B4 is the most common medium used in general organomineralization studies and has been used to assay or to characterize mineral precipitation potential. In an exercise for the optimization of the laboratory conditions of crystal precipitation in vitro, we used Bacillus subtilis 168 as a type strain and its isogenic mutants. While literature is mainly focused on observing generic precipitation, we investigated the requirement to obtain large crystals (≥1mm), which could be advantageous in wide-ranging implications for bioconsolidation of soil, sand, stone, and cementitious materials. Calcite crystals are visible on B4 agar plates within 7 days at 37˚C after inoculum of B. subtilis 168 strain. In this study we show that to form large crystals with a diameter ≥1mm several conditions must be met: i) Reduced amount of B4 medium into the Petri plate improve crystal formation. 55mm Petri plates contained only 4mL of B4 agar medium reached a plateau in 6 days at 37ºC. High moisture and presence of water condense would decrease crystal formation. ii) Inoculation of cells using a rod instead of a circular shaped spot. When the same number of B. subtilis cells was streaked, rod-shape biofilm significantly fostered crystal precipitation, while spot-shape prevented precipitation. iii) When more than one biofilm is present within the same plate, mutual interactions can affect precipitation in each biofilm. iv) Spherical nucleation sites are identified as initial step during the formation of large calcite crystal

Towards the Construction of a Multi-agent Approach for Discovering the Meaning of Natural Language Collaborative Conversations

On the one hand, natural language is the main communication media for humans. It has a complex construction, based on the diversity of meaning for words and expressions according to the context. On the other hand, computers are not prepared to handle this ambiguity. The present work aims at presenting a multi-agent approach for dealing with the problem of discovering the meaning of expressions written in Spanish, based on a flexible recovery system and Bayesian principles. At a first stage, agents are supposed to identify the role of the words composing a sentence. At a second stage, a second set of agents is supposed to coordinate among them in order to assemble a meaning. Our research forms part and contributes to the analysis of collaborative conversations among participants in a web-based collaborative learning environment. © 2008 IEEE

Space Storable Rocket Technology (SSRT) basic program

The Space Storable Rocket Technology Program (SSRT) was conducted to establish a technology for a new class of high performance and long life bipropellant engines using space storable propellants. The results are described. Task 1 evaluated several characteristics for a number of fuels to determine the best space storable fuel for use with LO2. The results indicated that LO2-N2H4 is the best propellant combination and provides the maximum mission/system capability maximum payload into GEO of satellites. Task 2 developed two models, performance and thermal. The performance model indicated the performance goal of specific impulse greater than or = 340 seconds (sigma = 204) could be achieved. The thermal model was developed and anchored to hot fire test data. Task 3 consisted of design, fabrication, and testing of a 200 lbf thrust test engine operating at a chamber pressure of 200 psia using LO2-N2H4. A total of 76 hot fire tests were conducted demonstrating performance greater than 340 (sigma = 204) which is a 25 second specific impulse improvement over the existing highest performance flight apogee type engines

Exopolymeric substances (EPS) from Bacillus subtilis: polymers and genes encoding their synthesis

Bacterial exopolymeric substances (EPS) are molecules released in response to the physiological stress encountered in the natural environment. EPS are structural components of the extracellular matrix in which cells are embedded during biofilm development. The chemical nature and functions of these EPS are dependent on the genetic expression of the cells within each biofilm. Although some bacterial matrices have been characterized, understanding of the function of the EPS is relatively limited, particularly within the Bacillus genus. Similar gaps of knowledge exist with respect to the chemical composition and specific roles of the macromolecules secreted by Bacillus subtilis in its natural environment. In this review, the different EPS from B. subtilis were classified into four main functional categories: structural (neutral polymers), sorptive (charged polymers), surface-active and active polymers. In addition, current information regarding the genetic expression, production and function of the main polymers secreted by B. subtilis strains, particularly those related to biofilm formation and its architecture, has been compiled. Further characterization of these EPS from B. subtilis remains a challenge

Educational activities for students and citizens supporting the One-Health approach on antimicrobial resistance

Antibiotic resistance is one of the biggest threats to global health, food security and development. Urgent action is needed at all levels of society to reduce the impact and spread of antibiotic resistance. For a more sustaining approach, education in children, college students, citizens and caregivers are essential. The One-Heath approach is a collaborative, multisectoral and transdisciplinary strategy in which, no single organizations or sector can address the issue of antimicrobial resistance at the human–environment interface alone. Within this strategy, education plays a central role. In this scoping review, we highlighted a range of learning activities on antibiotic resistance as part of the One-Health approach. In particular, those applications that can be introduced to a wide audience to help arrest the current crisis for the next generation. The review identifies a high number of teaching opportunities: board and role-play games, round tables, musicals, e-learning and environmental experiments to couple with more curricula and formal education to inform a diverse group of audiences

Mentorship and the Professional Development of Culturally Responsive Evaluators in the American Evaluation Association's Graduate Education Diversity Internship (GEDI) Program

In this study, we used Q methodology to investigate perspectives on mentorship among alumni of the Graduate Education Diversity Internship (GEDI) program. We asked participants to think retrospectively and give their opinion on the most important characteristics a GEDI mentor should have, based on what they would have liked or needed when they participated in the GEDI program. Three different perspectives on mentoring emerged from participants. They show that mentoring is not unidimensional; that perceptions and expectations of mentoring are defined to a great extent by the professional needs, background, and expectation of the participants. We suggest that the program takes those needs and expectations into consideration and use them as criteria for selecting mentors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108671/1/ev20093.pd

Condensation in an Economic Model with Brand Competition

We present a linear agent based model on brand competition. Each agent belongs to one of the two brands and interacts with its nearest neighbors. In the process the agent can decide to change to the other brand if the move is beneficial. The numerical simulations show that the systems always condenses into a state when all agents belong to a single brand. We study the condensation times for different parameters of the model and the influence of different mechanisms to avoid condensation, like anti monopoly rules and brand fidelity.Comment: Accepted in: International Journal of Modern Physics

Educational activities for students and citizens supporting the one-health approach on antimicrobial resistance

Antibiotic resistance is one of the biggest threats to global health, food security and development. Urgent action is needed at all levels of society to reduce the impact and spread of antibiotic resistance. For a more sustaining approach, education in children, college students, citizens and caregivers are essential. The One-Heath approach is a collaborative, multisectoral and transdisciplinary strategy in which, no single organizations or sector can address the issue of antimicrobial resistance at the human–environment interface alone. Within this strategy, education plays a central role. In this scoping review, we highlighted a range of learning activities on antibiotic resistance as part of the One-Health approach. In particular, those applications that can be introduced to a wide audience to help arrest the current crisis for the next generation. The review identifies a high number of teaching opportunities: board and role-play games, round tables, musicals, e-learning and environmental experiments to couple with more curricula and formal education to inform a diverse group of audiences