Similarities in control of mini-F plasmid and chromosomal replication in Escherichia coli

A Research Agenda for the Assessment and Management of Acute Behavioral Changes in Elderly Emergency Department Patients

Introduction

Agitation, mental illness, and delirium are common reasons for older adults to seek care in the emergency department (ED). There are significant knowledge gaps in understanding how to best screen older adults for these conditions and how to manage them. In addition, in areas where research has been performed, implementation has been slow. A working group convened to develop a set of high-priority research questions that would advance the understanding of optimal management of older adults with acute behavioral changes in the ED. This manuscript is the product of a breakout session on "Special Populations: Agitation in the Elderly" from the 2016 Coalition on Psychiatric Emergencies' first Research Consensus Conference on Acute Mental Illness.

Methods

Participants were identified with expertise in emergency medicine (EM), geriatric EM, and psychiatry. Background literature reviews were performed prior to the in-person meeting in four key areas: delirium; dementia; substance abuse or withdrawal; and mental illness in older adults. Input was solicited from all participants during the meeting, and questions were iteratively focused and revised, voted on, and ranked by importance.

Results

Fourteen questions were identified by the group with high consensus for their importance related to the care of older adults with agitation in the ED. The questions were grouped into three topic areas: screening and identification; management strategies; and the approach to delirium.

Conclusion

It is important for emergency physicians to recognize the spectrum of underlying causes of behavioral changes, have the tools to screen older adults for those causes, and employ methods to treat the underlying causes and ameliorate their symptoms. Answers to the identified research questions have great potential to improve the care of older adults presenting with behavioral changes.

Replication of mini-F plasmids during the bacterial division cycle

The cell-cycle replication patterns of two mini-F plasmids have been examined using the membrane-elution technique (to produce cells labelled at different times during the division cycle) and scintillation counting (for quantitative analysis of radioactivity incorporated into plasmid DNA). The mini-F plasmid pML31, which contains the oriV and oriS origins of replication, replicates in a cell-cycle-specific manner with a pattern and cell-cycle timing similar to the parental F plasmid. The mini-F plasmid pMF21, deleted for the region containing the oriV origin of replication, replicates more randomly throughout the division cycle. These results suggest that the oriV origin of replication may be related to cell-cycle-specific replication of the F plasmid.

Site-specific proteolysis of mini-F plasmid replication protein RepE destroys initiator function and generates an incompatibility substance

Plasmid F replication is controlled by a plasmid-specified Rep protein with both autorepressor and initiator functions. The mechanism by which these two functions of a Rep protein are balanced to achieve stable replication is unknown; however, we speculated in prior work that Rep protein modification could be involved. We report here that naturally proteolyzed F RepE protein has been detected and characterized. The processed molecule lost the first 17 N-terminal aminoacyl residues and initiator function but acquired increased specific DNA-binding affinity in the presence of Escherichia coli chromosomal DNA. When supplied in trans, the altered protein acts as an incompatibility substance and eliminates maintenance of F'lac. These findings indicate that protein processing has the potential to contribute to the overall control of DNA replication.

Replication patterns of multiple plasmids coexisting in Escherichia coli

The replication patterns of several plasmids were measured simultaneously during the cell division cycle of Escherichia coli B/r. F plasmids harboring oriS, both oriS and oriV, pSC101, and pBR322 were found to replicate at all stages of the cell division cycle with kinetics which were indistinguishable from one another and clearly different from the periodic synthesis of the minichromosomes pAL49 and pAL70.

Integrative suppression of dnaA(Ts) mutations mediated by plasmid F in Escherichia coli is a DnaA-dependent process

The thermosensitivity of dnaA(Ts) mutations can be suppressed by integration of plasmid F (integrative suppression). In the light of the recent finding that F requires DnaA protein for both establishment and maintenance, integrative suppression of 11 dnaA(Ts) mutations by a mini-F, pML31, integrated near oriC was examined. The plating efficiency of integratively suppressed strains was dnaA(Ts) allele-dependent and medium-dependent. The initiation capability of suppressed dnaA(Ts) strains lacking the oriC site and their F- counterparts was determined at various temperatures between 30 degrees C and 42 degrees C. The degree of integrative suppression measured by the initiation capability varied in a dnaA(Ts) allele-dependent manner. F-directed DNA replication was most affected by the dnaA(Ts) mutations mapping in the middle of the gene whereas oriC-dependent replication was most thermosensitive in strains carrying mutations mapping in the carboxy-terminal half of the gene. The results indicated that the integrative suppression by F plasmid is a DnaA-dependent process and suggested that the requirements for DnaA protein in the oriC-dependent replication and F replication processes are qualitatively different.