## 1 Introduction
This feature of curdlan is an exception to the general expectation that EPS production and biofilm formation in most bacteria are typically regulated by three primary mechanisms: quorum sensing, cyclic dinucleotides and small non-coding RNAs [38]. Considering that curdlan is a polymer of glucose that is destined for the cell exterior, it seems reasonable that the expression of genes that incorporates this high-energy molecule into an exopolysaccharideacharide should be highly regulated. So far, the only regulatory mechanisms governing curdlan production that have been reported operate at the level of transcription control. This is in contrast to another exopolysaccharideacharide produced by _agrobacteriumium_, succinoglycan, which does not appear to be regulated at the level of transcription [8]. Curdlan has been intensively studied to increase production and lower costs during fermentation [39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49]. Two of the major considerations for improving production and lowering the costs are the complex native regulation controlling production and the specific nutritional conditions required during fermentation. These two considerations are related, since the specific conditions required during fermentation drive up the cost of production. Generally, the native regulation serves to restrain curdlan production until certain specific conditions are met. These include low nitrogen, high carbon sources, generous phosphate levels, and high aeration [27]. Some strains of _agrobacteriumium_, e.g., the well-known plant pathogen _A. tumefaciens_ C58 that is used in plant genetic manipulations, do not produce detectable levels of curdlan [8], even though they carry the necessary genes (_crdASC_ and _crdR_). Other strains, such as the _agrobacteriumium_ sp. strain ATCC31749, have'suffered' from spontaneous mutations that appear to have partially relaxed the regulatory control over curdlan production, leading to high yields [6; 50]. Various genetic modifications of the strain ATCC31749 have generally resulted in not more than 10-50% improvement [35; 45; 47; 51]. For example, [PERSON] et al. [51] reported a mutant strain that was able to produce 76 g/1 curdlan in a stirred tank reactor after 120 h of cultivation, while the parent strain produced 64 g/1 under comparable conditions. One possible explanation was that a greater production rate of curdlan is not possible, i.e., that the production rate is limited by cellular metabolism capacities, uptake of carbon source, or lifetime of the bacterial cell. In that case, no amount of genetic engineering could greatly improve the yield. However, another possibility (tested in this study) was that a constitutive transcription of the _crdASC_ genes might yield higher levels of curdlan--an approach that has not been attempted. To state the hypothesis succinctly, if the native promoter Pcrd that controls the expression of the entire _crdASC_ gene cluster were to be replaced with a stronger, unregulated promoter, this might lead to a higher curdlan yield, given that curdlan production is highly dependent upon transcription control. Related to the question of whether increased transcription of the _crdASC_ genes would increase production is whether a stronger synthetic promoter would relax the requirement for specific conditions (e.g., high oxygen, low nitrogen) and support high curdlan production independently of the nutritional conditions. Thus far, there have been no reports in the literature where the region of the linear chromosome of _Agrobacteriumium_ carrying the _crdASC_ genes has been modified with the goal of increasing their expression. The key to engineering a higher transcription rate for the _crdASC_ gene cluster is the knowledge of suitable promoters capable of strong transcription in _agrobacteriumium_.