China 
Africa 
Explore chapters and articles related to this topic
Quorum Sensing
Published in Vineet Kumar, Vinod Kumar Garg, Sunil Kumar, Jayanta Kumar Biswas, Omics for Environmental Engineering and Microbiology Systems, 2023
Archisman Bhunia, Kumar Narayan, Abhilasha Singh, Asmeeta Sircar, Nivedita Chatterjee
Alongside the involvement of autoinducer AHL in gram-negative bacteria, the gram-positive bacteria involve segmented pathway framework for quorum sensing. The segment/component pathway involves AIPs that are synthesized ribosomally as initial pro-peptide structures and are later post-translationally modified to functional AIP molecules. Two key elements: HK at the membrane and the intracellular response regulatory (RR) receptors, are involved in this component pathway. Thus, it is commonly recognized as the two-component signal transduction pathway. It was initially identified in Lactococcus lactis and Streptococcus pneumoniae, and later in different strains of gram-positive bacteria. This pathway regulation is mediated through phosphorylation, which in turn leads to signal amalgamation in kinases that are controlled by environmental cues (Liu et al., 2018). Another pathway involved is a self-signaling pathway where the ribosomally synthesized and post-translationally modified AIPs are synthesized by SecA-dependent systems and activated under favorable parameters of modification. The key difference with the two-component pathway is that the AIPs, on reaching the threshold density gradient, are influxed inside the cell cytoplasm via an oligopeptide transporter system (Rutherford and Bassler, 2012). This regulation within the cascade of gene expression plays a crucial role in numerous colony-wide functions such as bioluminescence, conjugation, competence, sporulation, virulence, and biofilm formation.
Role of Microbes in Environmental Sustainability and Food Preservation
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Huang En, Ravi Kr. Gupta, Fangfei Lou, Sun Hee Moon
The production of lantibiotics is coordinately regulated by cellular events and the signal transduction pathway. For example, nisin biosynthesis is controlled by a typical two-component regulatory system (Chatterjee et al., 2005). The system comprises a histidine kinase (NisK) and a transcriptional response regulator (NisR). Nisin molecule is the signal for inducing the expression of the nis gene cluster. In the presence of nisin molecules, the membrane protein NisK transmits the signal to NisR. Then the activated NisR binds to nisA and nisF operators and thus triggers the transcription of the nisin gene cluster (Chatterjee et al., 2005). The production of other lantibiotics may be regulated by different mechanisms. For example, lacticin 481 production by Lactococcus lactis is induced through acidification resulting from lactic acid production (Hindré, Pennec, Haras, & Dufour, 2006).
Mechanisms of Bacterial Heavy Metal Resistance and Homeostasis
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Pallavee Srivastava, Meenal Kowshik
The widespread yybP-ykoY riboswitch family has been implicated in maintaining Mn2+ homeostasis in bacteria such as E. coli, B. subtilis, and Lactococcus lactis (Price et al., 2015; Dambach et al., 2015). The Mn2+-dependent transcription-ON riboswitch in L. lactis regulates the expression of YoaB, a P-type ATPase Mn2+ exporter. In the presence of elevated levels of Mn2+, this riboswitch selectively binds to the metal ion at its aptamer region based on its charge, intracellular free ionic concentration, ligand hardness, preferred coordination geometry, and ionic radius. Two phosphate rich pockets are created within the aptamer region that binds the Mn2+ only after the complete dehydration of the metal ion. This brings about the conformational changes that result in the expression of yoaB gene (Fig. 5), which is not expressed in the absence of Mn2+ (Price et al., 2015). Mn2+ sensing riboswitch present in E. coli and B. subtilis exhibit similar properties, except the gene regulated by these riboswitches is mntP gene that encodes the MntP manganese transporter (Dambach et al., 2015).
Heterologous expression of azurin from Pseudomonas aeruginosa in food-grade Lactococcus lactis
Published in Preparative Biochemistry and Biotechnology, 2019
Lactococcus lactis, generally recognized as safe (GRAS) microorganism by the American Food and Drug Administration (FDA), is a homofermentative gram-positive, a nonpathogenic and noninvasive bacterium.[10] It has been used in the production of fermented milk products for many years. Lactococcus lactis is also used as a host for the production of heterologous proteins in the food industry, biopharmaceuticals and vaccine research. Some heterologous proteins such as listeriolizine O,[11] β-galactosidase,[12] and pediocin[13] have been successfully produced in L. lactis. The most effective food-grade inducible expression system using L. lactis is nisin controlled gene expression (NICE) system. The food-grade L. lactis expression system has many advantages such as rapid growth, high safety, easy operation, and ideal carrier for heterologous proteins.[12,14] In this expression system, L. lactis NZ3900 strain, which was a deleted lacF gene, is used in combination with expression vector pNZ8149 containing a lacF gene, and lactose as a selection marker.[15]
Higher titer hyaluronic acid production in recombinant Lactococcus lactis
Published in Preparative Biochemistry and Biotechnology, 2018
Cansu Sunguroğlu, Dilber Ece Sezgin, Pınar Aytar Çelik, Ahmet Çabuk
As a Gram positive and homofermentative lactic acid bacterium, Lactococcus lactis, has been extensively used in fermentation of dairy products. Moreover, it has been increasingly used in modern biotechnological applications because of its GRAS (Generally Recognized as Safe) status.[13,20–23] Because L. lactis does not have any hyaluronidase activity, it has become a good candidate for recombinant HA production.[24]