Directed assembly of a bacterial quorum

Abstract

Many reports have elucidated the mechanisms and consequences of bacterial quorum sensing (QS), a molecular communication system by which bacterial cells enumerate their cell density and organize collective behavior. In few cases, however, the numbers of bacteria exhibiting this collective behavior have been reported, either as a number concentration or a fraction of the whole. Not all cells in the population, for example, take on the collective phenotype. Thus, the specific attribution of the postulated benefit can remain obscure. This is partly due to our inability to independently assemble a defined quorum, for natural and most artificial systems the quorum itself is a consequence of the biological context (niche and signaling mechanisms). Here, we describe the intentional assembly of quantized quorums. These are made possible by independently engineering the autoinducer signal transduction cascade of Escherichia coli (E. coli) and the sensitivity of detector cells so that upon encountering a particular autoinducer level, a discretized sub-population of cells emerges with the desired phenotype. In our case, the emergent cells all express an equivalent amount of marker protein, DsRed, as an indicator of a specific QS-mediated activity. The process is robust, as detector cells are engineered to target both large and small quorums. The process takes about 6 h, irrespective of quorum level. We demonstrate sensitive detection of autoinducer-2 (AI-2) as an application stemming from quantized quorums. We then demonstrate sub-population partitioning in that AI-2-secreting cells can 'call' groups neighboring cells that 'travel' and establish a QS-mediated phenotype upon reaching the new locale.

Electronic control of gene expression and cell behaviour in Escherichia coli through redox signalling

“…The plasmid pT5G was derived from a plasmid previously used for constitutive expression of DSRedExpress2 (refs 59, 60). First, a redundant HindIII restriction endonuclease site (AAGCTT) was deleted from plasmid pT5RT7G through plasmid PCR using primers HindIIIdel-F and HindIIIdel-R.…”

TumbleScore: Run and Tumble Analysis for Low Frame-Rate Motility Videos

“…Also, cheZ- cells were those transformed with pFZY1 to overproduce CheZ based on a peroxide chemical inducer, H 2 O 2 . All cells were also transformed with pT5RT7G , which confers constitutive egfp expression (20,24). These cells are thus very bright when imaged using fluorescence microscopy, allowing for superior contrast.…”

Incorporating LsrK AI‐2 quorum quenching capability in a functionalized biopolymer capsule

“…The use of reporter cells is an increasingly common means of verifying QS inhibition (Jha, Kavita, Westphal, Hartmann, & Schmitt‐Kopplin, ; McInnis & Blackwell, ). In addition, the quantity of AI‐2, produced by nanofactories in vitro (Fernandes et al, ) and as supplemented to cell cultures, has also been used as an indirect indicator of QS activity (Servinsky et al, ; Tsao et al, ). The final step in verification of the system involved using conditioned media from the AI‐2 producing E. coli BL21, incubating with the CT104 reporter cells, and then evaluating whether or not QS activity was altered (e.g., quorum quenching) via alteration of the naturally‐produced AI‐2.…”