Large-scale oxygen-enriched air (OEA) production from polymeric membranes for partial oxycombustion processes

Partial oxycombustion using Oxygen-Enriched Air (OEA), produced by air-gas separation with polymeric membranes, combined synergistically with CO2 capture technologies, reduced the overall energy cost of CO2 capture, and it is an exciting alternative to conventional CO2 capture technologies. An exhaustive review of polymeric membranes for this application is presented, where the best membranes showed permeability values in the range of 500-25,100 barrer and selectivities higher than 3.6. These membranes can produce OEA with oxygen molar concentrations of up to 45% for the retrofitting of large-scale power plants (~500 MWe) with partial oxycombustion. For OEA production, the polymeric membrane system is more efficient than the cryogenic distillation as the specific power consumption of the former is 43.96 kWh/ton OEA, while that of the latter is 49.57 kWh/ton OEA. This work proposes that the OEA produced by membranes feeds a partial oxy-combustion process integrated with calcium looping within a hybrid CO2 capture system. The energy consumption of the hybrid CO2 capture system proposed here is 6% lower than in the case in which OEA is produced from cryogenic distillation, which justifies the potential interest of using polymeric membranes for OEA production.Este ítem es la versión preprint del artículo. Se puede consultar la versión final aquí https://doi.org/10.1016/j.energy.2023.126697Junta de Andaluci

Characterisation of novel and complex mechanisms of antobiotic resistance using a proteomics approach

The problem of increasing rates of antibiotic resistance has become a global concern, particularly among multi drug resistant Gram-negative nosocomial pathogens. These organisms display non- susceptibility to the majority of routinely used antibiotics, causing infections which are more difficult to treat and increase the duration of patient recovery. Due to the plethora of resistance determinants and the molecular machinery which facilitates their dissemination, new strategies are required to investigate the mechanisms that confer antibiotic resistance. Proteomic techniques allow the global analysis of the expressed proteome, providing a more holistic view of the current physiological state of the bacterial cell. The techniques used in this investigation cover the separation, quantification and identification of proteins present in cellular extracts from resistant organisms. These included the use of 2-D electrophoresis, DIGE and LC-MS/MS mass spectrometry applied to multidrug resistant Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens and Acinetobacter baumannii. In summary, these investigations revealed that the Tol-Pal membrane protein system and susceptibilities to polymyxin antibiotics and biocides are altered upon acquisition of a resistance plasmid in E. coli. Furthermore, it revealed that non-carbapenemase-mediated carbapenem resistance in K. pneumoniae involved the loss of fimbriae proteins, the increased expression of OmpK26 and the resistance proteins EmrA and APH(3"), in addition to OmpK35/36 porin loss. The upregulation of a multi drug efflux pump in E. cloacae, A. baumannii and S. marcescens involved the differential regulation of many proteins, spanning a broad range of functional classes, including the MinCDE cell division inhibitors, iron acquisition proteins such as FepA and FhuA and proteins involved in biofilm and LPS formation such as PapC, LptD and GmhA. Overall this project has highlighted the complex and dynamic changes in protein expression upon acquisition of a resistance phenotype and the importance of using genetically related isolates when undertaking proteomic analyses. This work also emphasised the advantages of using proteomics for profiling the expression of resistance proteins, including the detection of specific enzymes, such as CTX-M ESBLs

Endogenous production and detoxification of a potent cytotoxin, nitric oxide, in Salmonella enterica serovar Typhimurium and Escherichia coli

Salmonella serovars are harmful enteric pathogens of economical and clinical importance that possess sophisticated strategies to rapidly adapt to various host (human and animal) and non-host (soil, water and industrial) environments. Nitrosative stress, in the form of RNS such as the potent cytotoxin NO, is an important stress in the Salmonella lifecycle. Salmonella is exposed to exogenous NO, produced by activated macrophages as part of the host immune response and to endogenous NO, produced during anaerobic nitrate respiration. Salmonella employs three known enzymes (HmpA, NrfA and NorVW) to detoxify NO to less toxic compounds, including the neuropharmacological agent and greenhouse gas N2O. The production of endogenous NO and N2O have been predominantly studied in denitrifying soil bacteria and have been widely neglected in enteric bacteria. Here, the physiological and molecular mechanisms involved in endogenous NO production and detoxification were examined in the pathogenic Salmonella enterica serovar Typhimurium and laboratory Escherichia coli (E. coli) strains. Significant differences in N2O production were observed between the two genera and between the tested E. coli strains, although they possess identical nitrate respiration systems. The reason for this was found to be transcriptional, with narG expression having the major impact. In addition, our results indicate that a weak nitrous oxide reductase exists in Salmonella; a process that was believed to be restricted to certain soil bacteria, archaea and fungi that possess the enzyme NosZ. Furthermore, the contribution of selected NsrR regulon genes, to endogenous N2O production of Salmonella was determined and revealed that HmpA and the Hcp-Hcr operon are both crucial for high N2O levels. These findings provide new insights into host-pathogen interactions, which could potentially lead to new treatment strategies for Salmonella infections, help to increase food safety and provide new mitigation strategies to reduce global warming

Biosensors for Environmental Monitoring

Real-time and reliable detection of molecular compounds and bacteria is essential in modern environmental monitoring. For rapid analyses, biosensing devices combining high selectivity of biomolecular recognition and sensitivity of modern signal-detection technologies offer a promising platform. Biosensors allow rapid on-site detection of pollutants and provide potential for better understanding of the environmental processes, including the fate and transport of contaminants.This book, including 12 chapters from 37 authors, introduces different biosensor-based technologies applied for environmental analyses

Optimal Membrane-Process Design (OMPD): A software product for optimal design of membrane gas separation processes

\u3cp\u3eThe optimal design of a membrane gas separation process requires minimizing several objective functions subject to nonlinear relationships among the optimizing variables. This article describes a novel software product, named Optimal Membrane-Process Design (OMPD), for the optimal design of membrane gas separation processes. The product generates several potential process design configurations and then searches the process design parameters and operating conditions spaces to arrive at optimal design specifications and operating conditions. It is able to consider every type and any number of operational, compositional, and economical objective functions in a computationally cost-effective manner. It calculates all Pareto optimal solutions in a single trial. It can optimize any number of membrane units arranged in multi-step and/or multi-stage configurations. It optimally places pairs of adjacent membrane units, either two-step or two-stage, while simultaneously considering several membrane types.\u3c/p\u3

Doctor of Philosophy

dissertationUrinary tract infections (UTIs) afflict millions of individuals yearly, constituting a tremendous global health-care burden. The primary causative agents of UTIs are the gram-negative, rod-shaped bacteria, uropathogenic Escherichia coli (UPEC). These pathogens are motile and adhesive, with a proclivity to colonize diverse niches within the urinary tract; including the kidneys, bladder, and ureters. In the bladder, UPEC grow to high levels and often associate with the superficial epithelial cells lining the lumen. UPEC can invade these superficial epithelial cells to form intracellular reservoir populations, which are thought to be a source of recurrent, or relapsing, infections. The susceptibility of these intracellular UPEC populations was tested using a panel of commonly prescribed antibiotics in a murine model of UTI. Intracellular UPEC were found to persist despite treatment with host cell-permeable antibiotics such as sparfloxacin and ciprofloxacin that effectively sterilize the urine. In a follow-up study, UPEC reservoir populations were more effectively targeted by treating infected bladders with chitosan, a chitin-based bladder exfoliant, prior to sparfloxacin treatment. Although chitosan administration prior to antibiotic treatment significantly decreased UPEC titers, mice still exhibited some relapsing UTIs, suggesting that reservoirs still persist either within the bladder or in other host tissue. To further elucidate mechanisms of bacterial persistence within the urinary tract, several underappreciated bacterial factors were examined that were hypothesized to affect UPEC virulence, stress resistance, and persistence. iv Bacterial, small, non-coding RNAs (sRNAs) are posttranscriptional regulators of gene expression in most prokaryotes and were shown to contribute to a wide variety of UPEC stress response and virulence cascades. In a follow-up study, the putative UPEC sRNA repertoire was defined using RNA-Seq technologies and bioinformatic analyses. Several novel, candidate sRNA molecules were identified and characterized, one of which seemingly repressed UPEC virulence in the murine UTI model. In a second approach to define regulators of UPEC pathogenic behaviors, the tRNA modifying enzyme MiaA was identified as a global regulator of UPEC stress response and virulence. MiaA adds a prenyl group to A-37, adjacent to the anticodon, in a subset of tRNAs to modulate ribosome fidelity and frameshifting. MiaA expression in UPEC was responsive to several environmental stresses and deletion or overexpression of MiaA interferes with the stress resistance and virulence properties of UPEC. Taken together, this thesis defines the robust nature and resilience of intracellular UPEC reservoir populations and delineates sRNAs and MiaA as important regulators of stress resistance and persistence within the host

Towards Understanding Helicase and Chaperone Activities in the RNA Degradosome

The E. coli RNA degradosome is a complex multi-enzyme machine which is central to the post-transcriptional regulation of the cell. Some of its functions include maturing and processing sRNA, rRNA, and tRNA, as well as degrading mRNA. The key components of the RNA degradosome include the endoribonuclease RNase E, the DEAD-box RNA helicase RhlB, the glycolytic enzyme enolase, and the phosphorolytic exoribonuclease PNPase. The degradosome has also been previously shown to associate with the RNA chaperone Hfq to form a small RNA guided machinery that targets defined transcripts. This thesis attempts to investigate several characteristics of the degradosome, including the importance of RhlB, the structure of a portion of the RNase E C-terminal domain that recruits enolase and helicase, and the association between Hfq, ChiX and the RNase E C-terminus. The thesis also explored structural details regarding the small domain of RNase E involved in both RNA binding and oligomerisation and its relationship to the RNA binding KH domains. Utilizing a point mutation in the DEAD box of RhlB, I have found increased RNA affinity to mutant RhlB, the potential structure of Hfq — an RNA chaperone — bound to the sRNA ChiX, and a structural correlation between the RNase E small domain and other KH domains. Preliminary models of Hfq and ChiX structure show a novel binding mode for class II sRNAs as the majority of ChiX associating with the distal face of Hfq. Bioinformatic studies reveal evolutionary roots between the KH domains and the RNase E small domain, supporting the hypothesis that the RNase E small domain may be involved in a novel mode of RNA binding and recognition

Activity of compounds isolated from Carpobrotus edulis on efflux pumps of bacteria and cancer cells

Introdução: A resistência aos antibióticos é um grave problema de saúde quer em Portugal quer a nível mundial. Nos dias de hoje, uma grande percentagem dos isolados clínicos de bactérias Gram-negativas é multi-resistente (MR) e, sempre que estudado, o fenótipo MR é mediado pela sobre-expressão de bombas de efluxo (BE). A sobre-expressão de bombas de efluxo em bactérias resulta da exposição destas a um antibiótico que, por vários processos, lhes confere um fenótipo MR. Contudo, o processo pelo qual a estirpe bacteriana desenvolve resistência durante a terapia com determinado antibiótico, ainda não foi completamente demonstrado em laboratório. Frequentemente, o grau de resistência dos isolados clínicos é muitas vezes superior à dose constante de antibiótico usada na terapia e atingida no plasma do paciente. Entre as Enterobacteriaceae, a principal BE pertence à família RND, na qual a energia necessária ao efluxo provém da força proto-motriz (PMF). Factores do meio envolvente, tais como, cálcio, pH ou glucose (fonte de energia), têm extrema influência nos mecanismos de retenção ou efluxo de compostos pela célula. Contudo, uma vez que o invólucro celular é o primeiro componente bacteriano a enfrentar alterações das condições do meio onde a bactéria se encontra, tais como alteração da pressão hidrostática, osmolaridade ou pressão antibiótica, é essencial compreender a generalidade dos processos envolvidos na aquisição de resistência. Assim, é urgente compreender como é que as condições do meio influenciam a composição da membrana celular e os seus mecanismos de efluxo. A primeira parte desta dissertação estuda o efeito dessas condições na composição da membrana externa e nas respostas celulares. Foi então estudado o efeito do stress provocado quer por aumentos crescentes na concentração de antibiótico, quer por passagens sucessivas da estirpe bacteriana em concentrações constantes de antibiótico, simulando o que acontece no paciente quando submetido a longos períodos de terapia com antibiótico. Moduladores do efluxo podem ser usados em terapia, conjuntamente com os antibióticos, de modo a aumentar o seu efeito terapêutico. A sua utilização começa a seraceite como uma nova abordagem terapêutica contra a multi-resistência. Deste modo a segunda parte desta tese foca a purificação e caracterização de compostos isolados da planta Carpobrotus edulis, cujo extracto metanólico mostrou, anteriormente, inibir BE bacterianas. Uma vez que foi já demonstrado existir uma relação entre BE de bactérias e de células cancerígenas, foi também estudado o efeito inibitório dos compostos purificados num dos transportadores com mais relevância em multi-resistência em células cancerígenas (P-gp). Métodos: Foram utilizados métodos de extracção de proteínas e electroforese para estudar a composição da membrana externa de células bacterianas cujo crescimento ocorreu em dois meios diferentes: sólido e líquido. O efeito da pressão antibiótica na expressão de BEs foi estudada através do crescimento de estirpes bacterianas em concentrações crescentes de antibiótico ou mantendo-as em concentrações de antibiótico constantes por longos períodos de tempo. No final das sucessivas passagens foi estudada a resposta celular a diferentes antibióticos na presença de moduladores de efluxo bem como os níveis de expressão de BEs por RT-PCR em tempo real. O efeito de moduladores de efluxo tais como CCCP, PAβN, verapamil ou fenotiazinas e os efeitos do cálcio, pH e fontes de energia foram estudados pelo método semi-automático que segue a acumulação ou efluxo de brometo de etidium pelas células bacterianas, em tempo real, nas condições aplicadas ao meio do ensaio experimental. O estudo das actividades in vitro dos compostos isolados de C. edulis em relação a estirpes de referência e outras multi-resistentes, que sobre-expressam determinadas BE, foi realizado por determinação das concentrações mínimas inibitórias dos compostos, bem como de outros antibióticos, aos quais as estirpes eram resistentes, na presença do composto. O método semi-automático atrás referido foi também utilizado no estudo destes compostos como moduladores de efluxo. A influência destes compostos na morte de estirpes bacterianas fagocitadas por macrófagos foi também estudada: ensaios ex vivo. Por fim, foi estudada a actividade antiproliferativa dos compostos isolados em linhas celulares cancerígenas bom como a sua capacidade de inibição da P-gp responsável pela multi-resistência nessas linhas celulares. Resultados: Durante este estudo foi observado que em meio líquido há maior expressão de uma proteína com 55kDa em oposição ao que acontece quando a bactéria cresce emmeio sólido. A simulação da resposta bacteriana durante a terapia pelos dois processos descritos, mostrou que a resposta bacteriana é dependente do processo de adaptação seguido. Os resultados desta dissertação sugerem, também, que o efluxo e a acumulação de EB por células de E. coli são dependentes do pH e de energia, os quais influenciam o desempenho da bomba de efluxo AcrAB. Esta BE depende da concentração periplasmática de protões para a sua activação. O efluxo é independente do pH do meio onde as células bacterianas cresceram, contudo, é dependente do pH do ensaio, o que sugere que a bactéria é capaz de se adaptar a diferentes condições do meio tais como pH ou agentes prejudiciais à sua sobrevivência. Devido à sua capacidade quelante, o composto CCCP foi usado a diferentes pH com o objectivo de compreender o papel da concentração protónica e da PMF no efluxo. O uso de CCCP juntamente com variações no pH, possibilitou a identificação dos principais tipos de sistemas de efluxo que respondem às diferentes condições do meio. Contudo, o composto PAβN interfere com o efluxo de EB, por competição com este, pelo sítio activo da bomba de efluxo (um KM para esta competição foi determinado). Os compostos isolados da planta C. edulis foram: ácido oleanólico, β-amirina, uvaol, catequina, epicatequina, MGDG e procianidina B5. Foi observado que estes compostos tinham diferentes actividades consoante o mecanismo de resistência característico de cada uma das estirpes em que a sua actividade foi estudada. Este facto está de acordo com os resultados obtidos para a resposta celular de bactérias, cuja multi-resistência foi obtida por diferentes mecanismos, perante o uso de moduladores. Os resultados obtidos sugerem que, de entre os compostos isolados, o composto uvaol foi o mais activo como modulador da actividade de efluxo, quer em células bacterianas quer em células cancerígenas. Também demonstrou uma actividade significativa contra Staphylococcus aureus intracelular. Conclusão: Uma proteína de 55kDa foi anteriormente descrita como factor de virulência. A mesma proteína encontrava-se menos expressa em bactérias cultivadas na presença de uma fenotiazina, um composto descrito como modulador de efluxo. Deste modo a acção destes compostos como adjuvantes terapêuticos pode dever-se à sua capacidade de reduzir a virulência de determinada estirpe. Deste modo, os resultadosobtidos, quando células bacterianas cresceram em meios líquido e sólido, são extremamente importantes pois podem indicar o motivo pelo qual infecções pelo mesmo organismo, mas por via de diferentes origens alimentares, apresentam diferentes graus de infecção e virulência para o paciente. A adaptação induzida por passagens sucessivas em meio com a mesma concentração de antibiótico sugere a presença de genes “mutantes” cuja actividade possibilita a sobrevivência celular em condições de “stress”, reduzindo o consumo de energia. De outro modo este seria mais elevado devido à sobre-expressão dos sistemas de efluxo, tal como acontece quando a bactéria é sujeita a passagens em concentrações crescentes de antibiótico. Os resultados desta dissertação também sugerem que a activação do efluxo, mediado pela bomba de efluxo AcrAB, é dependente da concentração protónica no periplasma. Assim, quando células de E. coli experimentam condições adversas causadas por agentes tóxicos, o efluxo é efectuado preferencialmente por transportadores do tipo ABC se o pH for maior que 7. O facto de o efluxo ser uma resposta independente do pH a que a estirpe cresceu, mas dependente do pH do meio em que o ensaio está a decorrer, sugere que a bactéria é capaz de se adaptar a diferentes pH do meio, tais como os que encontra durante o processo de infecção. Os mecanismos de efluxo dependentes de energia também variam com o pH. Deste modo a conjugação destes dois factores é muito importante para o estudo e compreensão da fisiologia e dos mecanismos de efluxo. As BEs que pertencem à família ABC têm uma função importante a pH 8, contudo a PMF é fundamental para o efluxo por via dos transportadores da família RND, como observado nos ensaios a pH 5. O uso de compostos que interferem com a PMF ou afectam directamente os sistemas de efluxo tem também um papel relevante no estudo dos mecanismos de efluxo e sua fisiologia. Os resultados obtidos com os compostos purificados da planta C. edulis, sugerem que esta planta contem compostos promissores com actividade antibacteriana e anticancerígena. É importante salientar que a abundância desta planta na orla marítima de Portugal faz com que a produção em larga escala dos seus constituintes seja fácil, o que é um factor essencial no desenvolvimento de quaisquer produtos a usar na prática clínica.Introduction: Resistance to antibiotics and chemotherapy is a major health problem in Portugal and also globally. Nowadays, a significant proportion of clinical Gram-negative isolates are multi-drug resistant (MDR) and whenever studied, the MDR phenotype has been shown to be mediated by over-expressed efflux pumps (EPs). The over-expression of bacterial EPs is known to result from their exposure to one antibiotic that in some manner renders the bacterium with an MDR phenotype. Nevertheless, the process by which the development of an MDR phenotype that occurs during the period the patient is being treated with an antibiotic has yet to be completly demonstrated in the laboratory. Moreover, the degree of resistance of the Gram-negative clinical isolate is often-times many fold greater than the constant concentration used in therapy and reached in the patient plasma. Among Enterobacteriaceae, the major EP belongs to the RND superfamily which is mainly driven by energy coming from the proton motive force (PMF). Environmental factors such as Calcium (Ca2+), pH or glucose (energy source) have major influence in the mechanisms of retention or efflux of compounds by the cell. However, because the cell envelope is the first bacterial cell component to face changes in the environmental conditions such as hydrostatic pressure, osmolarity or antibiotic pressure, it is essential to have an over-view of all the processes involved in the acquisition of resistance. Therefore it is worthy to understand how such environmental conditions influence the outer-membrane composition of the cell and its mechanism of efflux. The first part of this dissertation focuses on the effect of such environmental conditions, on the composition of the outer membrane and the cellular responses It was, then, studied the role of antibiotic-promoted stress via step-wise increasing concentrations of antibiotic or serial passages of the bacterial strain in the same concentration of antibiotic, simulating what happens in the patient when she/he is submitted to long periods of antibiotic therapy. Efflux modulators can be used in therapy together with antibiotics for improvement of antibiotic action. Their use starts to be widely accepted as a new approach for thetherapy of multi-drug resistance. Therefore, the second part of this dissertation focuses on the purification and characterization of compounds purified from the plant Carpobrotus edulis whose methanolic extract had been previously shown to inhibit MDR EPs of bacteria. Because it was previously shown by others the relationship between EP in bacteria and cancer cells, the purified compounds were also studied for their inhibitory activity on one of the major efflux pump transporters of cancer cells (P-gp). Methods: Methods of protein extraction and electrophoresis were employed to assess the composition of the outer membrane after the bacterial cells face two different kind of growth media: solid and liquid. The effect of the antibiotic pressure on the EP expression was studied by growing different bacterial strains under increasing concentration of antibiotic or maintaining them in the same concentration for longer periods of time. The progeny strains were then tested for their response to the antibiotics in the presence of EPI and for their EP expression by real time reverse transcription PCR (rtRT-PCR). The effect of efflux pump modulators such as CCCP, PAβN, verapamil, phenothiazines, and the modulating effects of calcium, pH and energy source were studied by the semi-automated ethidium bromide (EB) method that follows the accumulation or efflux of EB, on a real time manner, by the bacterial cells under the conditions applied to the media. The assessment of C. edulis compounds for in vitro activity against wild type bacterial strains and their counterpart strains that over-produce given EPs was conducted by determination of the minimum inhibitory concentration (MIC) of the purified compounds as well as for other antibiotics of reference for each strain in the presence of the compounds to be tested. The activity of the compounds as efflux modulators were also tested by the semi-automated EB method, already mentioned. The compounds were also assessed for their capacity to increase the killing activity of macrophages infected with bacterial strains: ex vivo activity. Finally, the purified compounds were tested for their antiproliferative effect on cancer cell lines and their capacity to inhibit the P-gp responsible for the multi-drug resistance in those cell lines.Results: During this study it was observed that in liquid medium a greater expression of a 55kDa protein takes place as opposed to Salmonella strains grown in solid medium. The simulation of the response of bacteria to the therapy with antibiotics through the two different adaptation processes showed that the bacterial response is dependent upon the method of adaptation to the antibiotic used. The results of this dissertation also suggest that efflux and accumulation of EB by E. coli strains are dependent on pH and energy that influence the performance of the AcrAB pump. This EP is dependent upon protons present in the periplasm for its activation. The efflux response is independent of the pH of growth of the bacteria whereas it is dependent on the pH of the assay, suggesting that bacteria are able to adapt to different environmental conditions such as pH and presence of noxious agents. Due to its capacity for binding protons, CCCP was used at different pH, in order to understand the role of protons and PMF on the efflux. The use of CCCP together with variations in the pH helped to identify the main types of efflux transporters that respond to the different environmental conditions. However, PAβN modulates efflux of ethidium bromide by competing with it for the site of extrusion of the pump (a KM was determined). Oleanolic acid, β-amyrin, uvaol, catechin, epicatechin, MGDG and procyanidin B5 were the compounds isolated from the plant C. edulis. It was observed that the activity of some of these compounds was differed according to the mechanisms of resistance that characterizes the different strains against which their activity was studied. This is in agreement with the results obtained for the response of the bacterial cell adapted through different mechanisms to the use of efflux modulators. The results suggest that the triterpene uvaol was the most active compound as an efflux modulator in bacteria and cancer cells. It also has significant activity against intracellular Staphylococcus aureus. Conclusion: A 55kDa protein was previously described as a virulence factor. The same protein had less expression when the bacteria were grown in presence of a phenothiazine, a compound described as an efflux modulator. Consequently, the action of these compounds as adjuvants may be due to their capacity to reduce the virulence of the strain. Therefore the results obtained for bacteria grown in solid and liquid mediaare of extreme importance because they can be an evidence for the reasons by which these compounds are described as helper compounds. They can also indicate why infections by the same organism but through different food sources have different degrees of infection and virulence on the patient. Adaptation caused by serial passages in the same concentration of antibiotic suggests the presence of “mutator” genes that allows the cell to survive under stress conditions and reduce energy consumption that would otherwise be higher with the over-expression of efflux systems as occurs when bacteria is exposed to step-wise increasing concentrations of antibiotic. The results of this dissertation also suggest that the AcrAB mediated efflux is dependent upon protons present in the periplasm for their activation. Hence, when E. coli faces stress conditions caused by a noxious agent, its extrusion would be preferentially performed by an ABC type transporter at pH greater than 7. The efflux response is independent on the pH of growth of the bacteria but dependent on the pH of the assay suggesting that bacteria are able to adapt to different conditions such as environmental pH that it has to face during the infection process in the human body. Energy dependent efflux mechanisms vary upon the pH and the conjunction of pH and glucose is an important tool in the study and understanding of the physiology and mechanisms of efflux. Efflux pumps belonging to the ABC superfamily have an important role in efflux at pH 8; however, PMF is essential for RND family mediated efflux as per the results obtained at pH 5. The use of compounds that interfere with the PMF or directly affect the efflux systems has also a relevant role in the study of the efflux mechanisms and their physiology. Based on the results obtained with compounds purified from C. edulis, this plant is a promising source for search of more effective antibacterial, antimycobacterial and anticancer compounds. It is worthy to mention that the extremely easy availability of this plant in the coast of Portugal makes it an outstanding raw material for large scale production of its constituents which is essential for the development of any products to be used in practical medicine