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Marfil-Santana Miguel David,O’Connor-Sánchez Aileen,Ramírez-Prado Jorge Humberto,De los Santos-Briones Cesar,López-Aguiar,Lluvia Korynthia,Rojas-Herrera Rafael,Lago-Lestón Asunción,Prieto-Davó Alejand 한국미생물학회 2016 The journal of microbiology Vol.54 No.11
The need for new antibiotics has sparked a search for the microbes that might potentially produce them. Current sequencing technologies allow us to explore the biotechnological potential of microbial communities in diverse environments without the need for cultivation, benefitting natural product discovery in diverse ways. A relatively recent method to search for the possible production of novel compounds includes studying the diverse genes belonging to polyketide synthase pathways (PKS), as these complex enzymes are an important source of novel therapeutics. In order to explore the biotechnological potential of the microbial community from the largest underground aquifer in the world located in the Yucatan, we used a polyphasic approach in which a simple, non-computationally intensive method was coupled with direct amplification of environmental DNA to assess the diversity and novelty of PKS type I ketosynthase (KS) domains. Our results suggest that the bioinformatic method proposed can indeed be used to assess the novelty of KS enzymes; nevertheless, this in silico study did not identify some of the KS diversity due to primer bias and stringency criteria outlined by the metagenomics pipeline. Therefore, additionally implementing a method involving the direct cloning of KS domains enhanced our results. Compared to other freshwater environments, the aquifer was characterized by considerably less diversity in relation to known ketosynthase domains; however, the metagenome included a family of KS type I domains phylogenetically related, but not identical, to those found in the curamycin pathway, as well as an outstanding number of thiolases. Over all, this first look into the microbial community found in this large Yucatan aquifer and other fresh water free living microbial communities highlights the potential of these previously overlooked environments as a source of novel natural products.
Omar Santos,Miguel Ramírez,Carlos Cuvas,Liliam Rodríguez-Guerrero,Hugo Romero,Patricio Ordaz 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.11
This paper deals with the robust control design for a class of time delay systems subject to unmatched disturbances and/or uncertain dynamics. For this, a specific Lyapunov-Krasovskii functional, the so called Attractive Ellipsoid concept and the dynamic programming algorithm for optimal control, are summarized to design the sub-optimal robust control law. Thus, the Lyapunov-Krasovskii candidate functional associated with specific Linear Matrix Inequality solution is aimed to guarantee the so called Ultimate Uniform Bounded-Stabilization. Furthermore, the sub-optimal robust control is achieved by minimizing a Hamilton-Jacobi-Bellman like equation, related to Lyapunov-Krasovskii type functional, respect to the admissible control. Hence, the robust and exponential stabilization is concluded for a perturbed and unperturbed time delay system, respectively. The theoretical results are illustrated on two numerical systems.
Laura Iztacihuatl Serrano Ángel,Daniel Segura,Jeiry Toribio Jiménez,Miguel Ángel Rodríguez Barrera,Carlos Ortuño Pineda,Yanet Romero Ramírez 한국미생물·생명공학회 2020 한국미생물·생명공학회지 Vol.48 No.2
The global carbon storage regulator (Csr) system is conserved in bacteria and functions as a regulator in the exponential and stationary phases of growth in batch culture. The Csr system plays a role in the central carbon metabolism, virulence, motility, resistance to oxidative stress, and biofilm formation. Although the Csr was extensively studied in Gram negative bacteria, it has been reported only in the control of motility in Bacillus subtilis among Gram positive bacteria. The goal of this study was to explore the role of the csrA gene of Bacillus licheniformis M2-7 on motility and the bacterial ability to use hydrocarbons as carbon source. We deleted the csrA gene of B. licheniformis M2-7 using the plasmid pCsr-L, harboring the spectinomycin cassette obtained from the plasmid pHP45-omega2. Mutants were grown on culture medium supplemented with 2% glucose or 0.1% gasoline and motility was assessed by electron microscopy. We observed that CsrA negatively regulates motility by controlling the expression of the hag gene and the synthesis of flagellin. Notably, we showed the ability of B. licheniformis to use gasoline as a unique carbon source. Our results demonstrated that CsrA is an indispensable regulator for the growth of B. licheniformis M2-7 on gasoline.