Bacteria sensing

Carboxyl groups of certain glutamate side chains in proteins that control bacterial chemotaxis are methylated reversibly to form methyl esters.130 This carboxylmethylation occurs as part of a reaction sequence by which the bacteria sense compounds that can serve as food or that indicate the presence of food... 

Bacteria sense spatial gradients of chemoattractants by measurements separated in time. A bacterium sets off in a random direction and, if the concentration of the chemoattractant has increased after the bacterium has been swimming for a period of time, the likelihood of tumbling decreases and the bacterium continues in roughly the same direction. If the concentration has decreased, the tumbling frequency increases and the bacterium tests other random directions. The... 

Protein methylation plays a role in chemotaxis - the process whereby bacteria sense a chemical concentration gradient in the medium and move either toward or away from it. Methylation may protect proteins by... 

Chemotaxis The process by which bacteria sense a concentration gradient of a particular substance in the medium and move either up or down the gradient. 

The autoinducer is a low molecular weight compound that is easily leached from the cells into the culture medium. By the propagation of bacterial cells, the concentration of the autoinducer in the medium increases. When the concentration reaches a certain threshold, the biosynthesis of bioluminescence system begins, and the bacteria become luminescent. The process is also called quorum sensing (Fuqua et al., 1994). 

Fuqua, W. C.,Winans, S. C.,and Greenberg, E. P. (1994). Quorum sensing in bacteria the LuxR-LuxI family of cell density-responsive transcriptional regulators./. Bacteriol. 176 269-275. 

Fe Bacteria/Archaea Electron transport/ Redox sensing [Pe3S,] [Pe,S,T -140 to -460 52... 

In contrast to common usage, the distinction between photosynthetic and respiratory Rieske proteins does not seem to make sense. The mitochondrial Rieske protein is closely related to that of photosynthetic purple bacteria, which represent the endosymbiotic ancestors of mitochondria (for a review, see also (99)). Moreover, during its evolution Rieske s protein appears to have existed prior to photosynthesis (100, 101), and the photosynthetic chain was probably built around a preexisting cytochrome be complex (99). The evolution of Rieske proteins from photosynthetic electron transport chains is therefore intricately intertwined with that of respiration, and a discussion of the photosynthetic representatives necessarily has to include excursions into nonphotosynthetic systems. 

Transport systems can be described in a functional sense according to the number of molecules moved and the direction of movement (Figure 41-10) or according to whether movement is toward or away from equilibrium. A uniport system moves one type of molecule bidirectionally. In cotransport systems, the transfer of one solute depends upon the stoichiometric simultaneous or sequential transfer of another solute. A symport moves these solutes in the same direction. Examples are the proton-sugar transporter in bacteria and the Na+ -sugar transporters (for glucose and certain other sugars) and Na -amino acid transporters in mammalian cells. Antiport systems move two molecules in opposite directions (eg, Na in and Ca out). 

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