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Data science is about deriving insight, learning and understanding from data. This process may be automated via the use of advanced algorithms or scaffolded cognitively via the use of graphs. While much emphasis is currently placed on machine learning, there is still much to learn about the role of the data scientist, in particular the thinking process by which he reaches conclusions. The thinking process of the data scientist needs to be scaffolded as the human brain is easily overwhelmed by many variables. Graphs are a form of data abstraction and constitute an essential part of the data scientist’s toolkit. Graphs are also a viable scaffold on which the data scientist may gain familiarity with data. But the process of extracting insight from graphs is not always a trivial or straightforward process; it requires interpretative logic as well. Generalizing from the example of a simple graph type, the Venn diagram, we discuss various logical fallacies that can be committed when interpreting a Venn diagram. Amidst various considerations that dictate how a graph should be tackled, we explain why context is most important, and should form the first guiding principle during data analysis.

Experiential learning is a key development area of artificial intelligence in education (AIEd). It aims to provide learners with intuitive environments for autonomous knowledge formation and discovery through interactive experiences. However, experiential learning in AIEd faces two main challenges. Firstly, measuring learning performances in unstructured and informal educational settings is difficult. Secondly, providing frequent or timely feedback on student performance is inefficient. To address these issues, this paper explores using natural language processing (NLP) and the tool for the automatic analysis of cohesion (TAACO) features as indicators of student performance in an experiential learning course. Both NLP and TAACO features were tested on a baseline CART decision tree (DT) machine learning (ML) model with and without a grade population distribution mask to predict student final scores at the end of the course. Our results show that (1), the use of a distribution specific Gaussian mask significantly increases prediction accuracy of the CART DT. (2), NLP and TAACO features provide high information value for ML prediction tasks. (3), the CART DT is able to accurately classify learner grade scores against human assessments.

This work aimed to investigate the promotive effect of Ag modification on C-TiO

The removal of five selected pharmaceutical compounds was investigated in a lab-scale anaerobic membrane bioreactor (AnMBR) treating synthetic sewage. Trimethoprim (Tmp) and sulfamethoxazole (Smx) were consistently removed at efficiencies of 94.2 ± 5.5%, and 67.8 ± 13.9%, respectively, while in contrast, only marginal removals of carbamazepine (Cbz) (0.3 ± 19.0%) and diclofenac (Dcf) (15.0 ± 7.2%) were achieved. Finally, three distinct stages of triclosan (Tcs) removal were observed: 82.3 ± 15.0% within the first 10 days; 54.4 ± 10.4% in the following 30 days; and 31.4 ± 12.6% in the last 30 days. Adsorption to the sludge was the major contributing factor for its initial high removal. When powdered activated carbon (PAC) was added to the AnMBR, the removal of all five pharmaceuticals improved, especially for Smx and Tcs, which showed removal efficiencies of 95.5 ± 4.6% and 93.2 ± 6.6%, respectively. Higher removals of Cbz (92.4 ± 5.3%) and Dcf (82.6 ± 11.1%) were also observed, but only within the initial 5 days of PAC addition, and enhancement in their biotransformation by PAC adsorption was determined to be the major contributing factor for these improved removals.

This study discovered a strong correlation between the autoinducer-2 (AI-2)-mediated quorum sensing (QS) with the performance of a submerged anaerobic membrane bioreactor during its recovery from a pentachlorophenol (PCP) shock: a decrease in AI-2 levels coincided with a reduction in volatile fatty acid concentrations, and corresponded significantly to a decrease in the relative abundance of Firmicutes, and to an increase in the relative abundance of Bacteroidetes and Synergistetes. Further batch experiments with the addition of an AI-2-regulating Escherichia coli mutant culture showed that a reduction in AI-2 levels resulted in the highest biogas production rate during a PCP shock. In contrast, an increase in AI-2 levels via addition of the E. coli wild type strain or an AI-2 precursor showed no obvious effects on biogas production. These results suggest that the AI-2 level in anaerobic sludge was governed primarily by Firmicutes, and the AI-2-mediated QS partially regulates the toxic shock response of anaerobic sludge via tuning the activities of Firmicutes and Synergistetes. A decrease in the AI-2 level might reduce acetogenesis and favor hydrogenotrophic methanogenesis, thus resulting in less VFA accumulation and higher methane production during the PCP shock. This study is the first of this type that exploits the role of quorum sensing in the toxic shock response of anaerobic sludge; it demonstrates a novel approach to shortening the recovery period of anaerobic processes via manipulating the AI-2-mediated QS. National Research Foundation (NRF) The project was supported and administrated by the Environment & Water Industry Programme Office (EWI) for and on behalf of the National Research Foundation Board (NRF), Singapore (EWI-IRIS-0807). The project was also supported by the Shantou University Scientific Research Foundation for Talents (No.: NTF16015) and the National Natural Science Foundation of China (No.: 51750110514).

Artificial intelligence (AI) is profoundly changing biotechnological innovation. Beyond direct application, it is also a useful tool for adaptive learning and forging new conceptual connections within the vast network of knowledge for the advancement of biotechnology. Here, we discuss a new paradigm for biotechnology education that involves coevolution with AI. Accepted version

Biological wastewater treatment processes (WWTPs), by nature of their reliance on biological entities to degrade organics and sometimes remove nutrients, are vulnerable to toxicants present in their influent. Various toxicity measurement methods have been adopted for biological WWTPs, but most are performed off-line, and cannot be adapted to on-line monitoring tools to provide an early warning for WWTP operators. However, the past decade has seen a rapid expansion in the research and development of biosensors that can be used for toxicity assessment of aquatic environments. Some of these biosensors have also been shown to be effective for use in biological WWTPs. Nevertheless, more research is needed to: examine the sensitivity of assays and sensors based on single organisms to various toxicants and develop a matrix of biosensors or a biosensor incorporating multiple organisms that can protect WWTPs; test the micro fuel cell (MFC)-based biosensors with real wastewaters and correlate the results with the well-established oxygen uptake rate (OUR)-based or CH4-based toxicity assay; and, develop advanced data processing methods for interpreting the results of on-line toxicity sensors in real WWTPs to reduce the noise due to the normal fluctuation in influent quality and quantity.

Several powdered and granular activated carbons (PACs and GACs) were tested for adsorption of pentachlorophenol (PCP) in bench-scale anaerobic digestion reactors to control the toxicity of PCP to acetoclastic methanogenesis. Results showed that the adsorption capacities of PAC were reduced by 21–54%, depending on the PAC addition time, in the presence of the methanogenic sludge compared to the controls without sludge. As a preventive measure, PAC at a low dose of 20% (mass ratio to the VSS) added 24 h prior to, or simultaneously with, the addition of PCP could completely eliminate the toxic effects of PCP. At the same dose, PAC also enabled methanogenesis to recover immediately after the sludge had been exposed to PCP for 24 h. GAC was not effective in enabling the recovery of methanogenesis due to its slow adsorption kinetics; however, at a dose of 80% it could partially ameliorate the toxic shock of PCP. NRF (Natl Research Foundation, S’pore) Accepted version

Fifty strains representing 38 species of the genus Legionella were examined for biofilm formation on glass, polystyrene, and polypropylene surfaces in static cultures at 25°C, 37°C, and 42°C. Strains of Legionella pneumophila , the most common causative agent of Legionnaires' disease, were found to have the highest ability to form biofilms among the test strains. The quantity, rate of formation, and adherence stability of L. pneumophila biofilms showed considerable dependence on both temperature and surface material. Glass and polystyrene surfaces gave between two- to sevenfold-higher yields of biofilms at 37°C or 42°C than at 25°C; conversely, polypropylene surface had between 2 to 16 times higher yields at 25°C than at 37°C or 42°C. On glass surfaces, the biofilms were formed faster but attached less stably at 37°C or 42°C than at 25°C. Both scanning electron microscopy and confocal laser scanning microscopy revealed that biofilms formed at 37°C or 42°C were mycelial mat like and were composed of filamentous cells, while at 25°C, cells were rod shaped. Planktonic cells outside of biofilms or in shaken liquid cultures were rod shaped. Notably, the filamentous cells were found to be multinucleate and lacking septa, but a recA null mutant of L. pneumophila was unaffected in its temperature-regulated filamentation within biofilms. Our data also showed that filamentous cells were able to rapidly give rise to a large number of short rods in a fresh liquid culture at 37°C. The possibility of this biofilm to represent a novel strategy by L. pneumophila to compete for proliferation among the environmental microbiota is discussed.

Some promoters, including the DmpR-controlled sigma(N)-dependent Po promoter, are effectively rendered silent in cells lacking the nutritional alarmone (p)ppGpp. Here we demonstrate that four mutations within the housekeeping sigma(D)-factor can restore sigma(N)-dependent Po transcription in the absence of (p)ppGpp. Using both in vitro and in vivo transcription competition assays, we show that all the four sigma(D) mutant proteins are defective in their ability to compete with sigma(N) for available core RNA polymerase and that the magnitude of the defect reflects the hierarchy of restoration of transcription from Po in (p)ppGpp-deficient cells. Consistently, underproduction of sigma(D) or overproduction of the anti-sigma(D) protein Rsd were also found to allow (p)ppGpp-independent transcription from the sigma(N)-Po promoter. Together with data from the direct effects of (p)ppGpp on sigma(N)-dependent Po transcription and sigma-factor competition, the results support a model in which (p)ppGpp serves as a master global regulator of transcription by differentially modulating alternative sigma-factor competition to adapt to changing cellular nutritional demands.

The Pseudomonas-derived sigma54-dependent regulator DmpR has an amino-terminal A-domain controlling the specificity of activation by aromatic effectors, a central C-domain mediating an ATPase activity essential for transcriptional activation and a carboxy-terminal D-domain involved in DNA binding. In the presence of aromatic effectors, the DmpR protein promotes transcription from the -24, -12 Po promoter controlling the expression of specialized (methyl)phenol catabolic enzymes. Previous analysis of DmpR has led to a model in which the A-domain acts as an interdomain repressor of DmpR's ATPase and transcriptional promoting property until specific aromatic effectors are bound. Here, the autonomous nature of the A-domain in exerting its biological functions has been dissected by expressing portions of DmpR as independent polypeptides. The A-domain of DmpR is shown to be both necessary and sufficient to bind phenol. Analysis of phenol binding suggests one binding site per monomer of DmpR, with a dissociation constant of 16 microM. The A-domain is also shown to have specific affinity for the C-domain and to repress the C-domain mediated ATPase activity in vitro autonomously. However, physical uncoupling of the A-domain from the remainder of the regulator results in a system that does not respond to aromatics by its normal derepression mechanism. The mechanistic implications of aromatic non-responsiveness of autonomously expressed A-domain, despite its demonstrated ability to bind phenol, are discussed.

Pseudomonas-derived regulators DmpR and XylR are structurally and mechanistically related σ54-dependent activators that control transcription of genes involved in catabolism of aromatic compounds. The binding of distinct sets of aromatic effectors to these regulatory proteins results in release of a repressive interdomain interaction and consequently allows the activators to promote transcription from their cognate target promoters. The DmpR-controlled Po promoter region and the XylR-controlled Pu promoter region are also similar, although homology is limited to three discrete DNA signatures for binding σ54RNA polymerase, the integration host factor, and the regulator. These common properties allow cross-regulation of Pu and Po by DmpR and XylR in response to appropriate aromatic effectors. In vivo, transcription of both the DmpR/Po and XylR/Pu regulatory circuits is subject to dominant global regulation, which results in repression of transcription during growth in rich media. Here, we comparatively assess the contribution of (p)ppGpp, the FtsH protease, and a component of an alternative phosphoenolpyruvate-sugar phosphotransferase system, which have been independently implicated in mediating this level of regulation. Further, by exploiting the cross-regulatory abilities of these two circuits, we identify the target component(s) that are intercepted in each case. The results show that (i) contrary to previous speculation, FtsH is not universally required for transcription of σ54-dependent systems; (ii) the two factors found to impact the XylR/Pu regulatory circuit do not intercept the DmpR/Po circuit; and (iii) (p)ppGpp impacts the DmpR/Po system to a greater extent than the XylR/Pu system in both the nativePseudomonas putidaand a heterologousEscherichia colihost. The data demonstrate that, despite the similarities of the specific regulatory circuits, the host global regulatory network latches onto and dominates over these specific circuits by exploiting their different properties. The mechanistic implications of how each of the host factors exerts its action are discussed.

This work explored strontium titanate ferrite (SrTi1−xFexO3−δ or STFx in short) metal oxide as an effective antibacterial agent and investigated its bactericidal mechanism. The perovskite STFx nanoparticles (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) were successfully synthesized with high energy ball milling approach. The feasibility of utilizing this material for antibacterial application was studied on Escherichia coli (E. coli) in the presence of dispersed STF0.8 nanoparticles in water. Excellent bactericidal effect has been observed by killing all the E. coli (∼105 CFU/mL) within 15 min in both light and dark conditions, excluding photocatalysis as the major contributing mean of bactericidal effect. Mechanism study via surface charge characterization, fluorescence microscope observation, inductively coupled plasma measurement and SEM examination has revealed that the positive surface charge, high pH environment, Sr2+ dissociation and nano-size of STF0.8 metal oxide could have collectively contributed to its excellent bactericidal effect. These results have increased the potential to apply STFx in water purification for microorganism destruction. ASTAR (Agency for Sci., Tech. and Research, S’pore)

Transcription from the Pseudomonas CF600-derived ς 54 -dependent promoter Po is controlled by the aromatic-responsive activator DmpR. Here we examine the mechanism(s) by which integration host factor (IHF) stimulates DmpR-activated transcriptional output of the Po promoter both in vivo and in vitro. In vivo, the Po promoter exhibits characteristics that typify many ς 54 -dependent promoters, namely, a phasing-dependent tolerance with respect to the distance from the regulator binding sites to the distally located RNA polymerase binding site, and a strong dependence on IHF for optimal promoter output. IHF is shown to affect transcription via structural repercussions mediated through binding to a single DNA signature located between the regulator and RNA polymerase binding sites. In vitro, using DNA templates that lack the regulator binding sites and thus bypass a role of IHF in facilitating physical interaction between the regulator and the transcriptional apparatus, IHF still mediates a DNA binding-dependent stimulation of Po transcription. This stimulatory effect is shown to be independent of previously described mechanisms for the effects of IHF at ς 54 promoters such as aiding binding of the regulator or recruitment of ς 54 -RNA polymerase via UP element-like DNA. The effect of IHF could be traced to promotion and/or stabilization of open complexes within the nucleoprotein complex that may involve an A+T-rich region of the IHF binding site and promoter-upstream DNA. Mechanistic implications are discussed in the context of a model in which IHF binding results in transduction of DNA instability from an A+T-rich region to the melt region of the promoter.

The Pseudomonas derived sigma(54)-dependent DmpR activator regulates transcription of the (methyl)phenol catabolic dmp-operon. DmpR is constitutively expressed, but its transcriptional promoting activity is positively controlled in direct response to the presence of multiple aromatic effectors. Previous work has led to a model in which effector binding by the amino-terminal region of the protein relieves repression of an intrinsic ATPase activity essential for its transcriptional promoting property. Here, we address whether the observed differences in the potencies of the multiple effectors (i) reside at the level of different aromatic binding sites, or (ii) are mediated through differential binding affinities; furthermore, we address whether binding of distinct aromatic effectors has different functional consequences for DmpR activity. These questions were addressed by comparing wild type and an effector specificity mutant of DmpR with respect to effector binding characteristics and the ability of aromatics to elicit ATPase activity and transcription. The results demonstrate that six test aromatics all share a common binding site on DmpR and that binding affinities determine the concentration at which DmpR responds to the presence of the effector, but not the magnitude of the responses. Interestingly, this analysis reveals that the novel abilities of the effector specificity mutant are not primarily due to acquisition of new binding abilities, but rather, they reside in being able to productively couple ATPase activity to transcriptional activation. The mechanistic implications of these findings in terms of aromatic control of DmpR activity are discussed.

A high-throughput microfluidic poly-(dimethylsiloxane) biochip was developed to quantify bacterial adhesion to single host cells by real-time PCR assay. The biochip is simply structured with a two-dimensional array of 900 micro-wells, one inlet, and one outlet micro-channels. Isolation of single infected host cells into the individual micro-wells of the biochip was achieved by one-step vacuum-driven microfluidics. The adhered bacterial cells were then quantified by direct on-chip real-time PCR assay with single-bacterium-detection sensitivity. The performance of this microfluidic platform was demonstrated through profiling of the association of a common bacterial pathogen, Pseudomonas aeruginosa, to single host human lung epithelial A549 cells, revealing an adherence distribution that has not been previously reported. This microfluidic platform offers a simple and effective tool for biologists to analyze pathogen-host interaction at the single-cell level without the necessities of fluorescence labeling. The chip can similarly be used for other PCR-based applications requiring single-cell analysis.

This work aimed to investigate the promotive effect of Ag modification on C-TiO2 for visible light photocatalytic disinfection of microorganisms. Ag/C-TiO2 was prepared by a facile one-step synthesis approach through thermal oxidation of AgNO3-impregnated TiC precursor. The self-doped carbon exists as both interstitial and substitutional carbon to collectively enhance the visible light photocatalytic absorption. The loaded silver nanoparticles were uniformly distributed on the TiO2 surface in the Ag0 metallic state, further enhancing the visible light absorption due to surface plasmon resonance yet inhibiting the charge carrier recombination by conduction band electron trapping. The band structure and a tentative visible light photocatalytic disinfection mechanism of Ag/C-TiO2 with four pathways were thus proposed, and the enhanced visible light photocatalytic performance was demonstrated for disinfection of Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) in comparison with C-TiO2. This improvement was more pronounced with increasing Ag loading in the range of 0.5–5.0 wt%, which can be attributed to the improved visible light absorption and good charge carrier separation due to Ag modification as well as to the inherent bactericidal effect of metallic Ag. ASTAR (Agency for Sci., Tech. and Research, S’pore)

Purification of nucleic acids from a low quantity of bacterial cells in minute volume is important in many clinical and biological applications. We developed a novel microfluidic liquid phase nucleic acid purification chip to selectively isolate DNA or RNA from bacterial cells in the range of 5000 down to a single cell in the sample volume of 1 μl or 125 nl, which can be directly put through on-chip quantitative PCR assay. The aqueous phase bacterial lysate was isolated in an array of microwells, after which an immiscible organic (phenol-chloroform) phase was introduced in a headspace channel connecting the microwell array. Continuous flow of the organic phase increases the interfacial contact with the aqueous phase to achieve purification of target nucleic acid through phase partitioning. Significantly enhanced nucleic acid recovery yield, up to 10 fold higher, was achieved using the chip-based liquid phase nucleic acid purification technique compared to that obtained by the conventional column-based solid phase nucleic acid extraction method. One step vacuum-driven microfluidics allowed an on-chip quantitative PCR assay to be carried out in the same microwells within which bacterial nucleic acids were isolated, avoiding sample loss during liquid transfer. Using this nucleic acid purification device set in a two-dimensional (2D) array format of 900 microwells, it was demonstrated for the first time that high-throughput extraction of RNA couple with direct on-chip PCR analysis from single bacterial cells could be achieved. Our microfluidic platform offered a simple and effective solution for nucleic acid preparation, which can be integrated for automated bacterial pathogen detection and high throughput transcriptional profiling.

The cytotoxicity of benzene (BZ) and its major metabolites phenol (PHE), hydroquinone (HQ), catechol (CAT), 1,4-benzoquinone (BQ), 1,2,4-benzenetriol (BT), trans,trans-muconic acid (ttMA) and S-phenylmercapturic acid (S-PMA) was assessed by exposing Chinese Hamster Ovary (CHO) cells to these compounds. Benzene was the least toxic (LD50 = 20 mM), while BQ showed the highest potency (LD50 = 10 microM), followed by HQ (LD50 = 40 microM). It was found that the trend of cytotoxicity was: BQ > HQ > > CAT > ttMA > BT > S-PMA > > PHE > BZ. 1,4-Benzoquinone and HQ also demonstrated considerable ability to induce DNA strand breaks in CHO cells, which was assayed using the fluorimetric analysis of DNA unwinding. The other metabolites were unable to cause DNA strand breaks. When HQ was administered in combination with other metabolites, no synergism was observed in the induction of DNA strand breaks. From these results, it can be seen that BQ and HQ are the most bioreactive species among the benzene metabolites when tested on CHO cells. Differences between the results obtained in our study and other studies were discussed.

Pseudomonas putida P35X (NCIB 9869) metabolises phenol and cresols via a chromosomally encoded meta-cleavage pathway. A 13.4-kb fragment of the chromosome involved in encoding phenol catabolism was cloned and characterized. Deletion analysis and nucleotide sequencing of a 6589-bp region, in conjunction with enzyme assays, were used to identify the phhKLMNOP genes encoding the phenol hydroxylase, the phhB gene encoding catechol 2,3-dioxygenase (EC 1.13.11.2) and the phhQ gene that encodes a small ferredoxin-like protein. The genes are organised in an operon-like structure, in the order phhKLMNOPQB, and the deduced amino-acid sequences share high homology (68.3-99.7%) with those of the plasmid-encoded genes dmpKLMNOPQB of Pseudomonas sp. strain CF600. Genetic evidence is presented that the difference in the growth substrate ranges of Pseudomonas P35X and CF600 are due to the effector activation specificities of the regulators of these systems, rather than the substrate specificities of the catabolic enzymes.

When studying interspecies interactions in a bacterial consortium, it may be desirable to analyze one species' transcriptional response as influenced by the other species. We developed a dual fluorescence system of Escherichia coli for Fluorescence-Activated Cell Sorter (FACS)-based analysis for such a purpose. First, we generated E. coli SCC1 strain, which constitutively expresses green fluorescent protein (GFP), but otherwise showed no observable difference from the parent strain MG1655 with respect to morphology, growth, and FACS-analyzed side- and forward-scatter profiles. Next, to analyze transcriptional response, plasmids carrying promoters of interest fused to a red fluorescent protein (AsRed2) reporter, were introduced into strain SCC1. Quantification of promoter activities of araB, lacZ, fadB and rpoE via AsRed2 reporter verified that the induction levels are similar between MG1655 and SCC1 strains. In mixtures and co-cultures, GFP expression of E. coli SCC1 allowed it to be separated from non-E. coli species by FACS to purity levels of 96.7-100.0%. When a mixture of E. coli SCC1 carrying promoter-AsRed2 fusion and a non-E. coli strain was analyzed by FACS, it enabled (i) distinction of E. coli SCC1 from the non-E. coli strain, (ii) analysis of the E. coli promoter activity via AsRed2 expression and (iii) identification of transcriptional heterogeneity within the E. coli population. Co-cultures of E. coli SCC1 with Klebsiella pneumoniae and/or Enterococcus faecalis analyzed by FACS showed that E. coli fadB and rpoE transcription were differentially influenced by partner species.

Transcription from the Pseudomonas-derived sigma 54-dependent Po promoter of the dmp operon is mediated by the aromatic-responsive regulator DmpR. However, physiological control is superimposed on this regulatory system causing silencing of the DmpR-mediated transcriptional response in rich media until the transition between exponential and stationary phase is reached. Here, the positive role of the nutritional alarmone (p)ppGpp in DmpR regulation of the Po promoter has been identified and investigated in vivo. Overproduction of (p)ppGpp in a Pseudomonas reporter system was found to allow an immediate transcriptional response under normally non-permissive conditions. Conversely (p)ppGpp-deficient Escherichia coli strains were found to be severely defective in DmpR-mediated transcription, demonstrating the requirement for this metabolic signal. A subset of mutations in the beta, beta' and sigma 70 subunits of RNA polymerase, which confer prototrophy on ppGpp0 E. coli, was also found to restore specific DmpR-mediated transcription from Po, suggesting that the metabolic signal is mediated directly through the sigma 54-RNA polymerase. These data provide a direct mechanistic link between the physiological status of the cell and expression from sigma 54 promoters.

Transcription from Pseudomonas-derived -24, -12 Po promoter of the pVI150-encoded dmp operon is mediated by the sigma 54-dependent DmpR activator in response to the presence of aromatic pathway substrates in the medium. However, global regulatory mechanisms are superimposed on this regulatory system so that the specific response to aromatic effectors is absent in cultures until the stationary phase is reached. Here we genetically dissect the system to show that the growth phase response is faithfully mimicked by a minimal system composed of the dmpR regulatory gene and the Po promoter regulatory region and can be reproduced in heterologous Escherichia coli. Using this system, we show that the growth phase-dependent DmpR-mediated response to aromatic compounds is limited to fast-growing cultures. Thus, during exponential growth of cultures in minimal media containing different carbon sources, the response to aromatics is immediate, while the response is suppressed in cultures grown on rich media until the exponential-to-stationary phase transition. Elements known to be involved in the DmpR-mediated transcription from Po were analyzed for the ability to influence the growth phase response. Most dramatically, overexpression of DmpR was shown to completely abolish the growth phase response, suggesting that a negatively acting factor may mediate this level of regulation. The possible mechanism of action and integration (of the specific regulation of the dmp operon-encoded catabolic enzymes with the physiological status of the bacteria are discussed.