Dr.T.V.Rao MD<br />Socio-microbiologybiofilms and quorum sensing in infectious diseases<br />Dr.T.V.Rao MD<br />1<br />
Sociomicrobiology" is part of the broader discipline "Microbiology", the study of organisms (bacteria, yeast, molds, viruses and protists) that cannot be observed with the naked eye, but having critical mechanisms for propagation.<br />Sociomicrobiology<br />Dr.T.V.Rao MD<br />2<br />
Sociomicrobiology <br />The term "sociomicrobiology" was introduced by Matt Parsek & Peter Greenberg in 2005 (Trends in Microbiology, 13:27-33) and refers to the group behavior of micro-organisms, Two topics that form the core of sociomicrobiological research are microbial biofilm formation and cell-cell communication (quorum sensing).<br />Dr.T.V.Rao MD<br />3<br />
4<br />Introduction<br /><ul><li>Quorum sensing is cell to cell signaling mechanism that enables the bacteria to collectively control gene expression.
This type of bacterial communication is achieved only at higher cell densities.
Bacteria release various types of molecules called as auto inducers in the extracellular medium, these molecules are mediators of quorum sensing.
When concentration of these signaling molecules exceed a particular threshold value, these molecules are internalized in the cell and activate particular set of genes in all bacterial population, such as genes responsible for virulence, competence, stationary phase etc .</li></ul>Dr.T.V.Rao MD<br />
The study of group behavior in microbes<br />• Debate over environmental vs. genetic determinates<br />• Biofilms and quorum sensing<br />• Model for dissecting social behavior at a genetic level<br />Sociomicrobiology advances the understanding microbes<br />Dr.T.V.Rao MD<br />5<br />
Bacteria are dynamic creatures<br />Bacteria are dynamic creatures that are able to regulate their metabolism and lifestyle in response to a variety of environmental cues. These cues include changes in their chemical, physical, and biological surroundings. In recent decades, microbiologists have come to appreciate that bacteria are even able to recognize changes in their own population density. Cell density-dependent regulation has been termed "quorum sensing."<br />iosynthetic and regulatory prodigiosin mutants of Serratia<br />Dr.T.V.Rao MD<br />6<br />
Microbes run in our body as normal flora<br />Microbes run much of our body. The human micro biome in our gut, mouth, skin, and elsewhere, harbors 3,000 kinds of bacteria with 3 million distinct genes. (Our own cells struggle by on only 18,000 genes or so.)…This biotech century will be microbe enhanced and maybe microbe inspired….Confronting a difficult problem we might fruitfully ask, “What would a microbe do?”<br />Dr.T.V.Rao MD<br />7<br />
Models to understand biology of sociality<br />To develop new medicines to treat devastating bacterial infections<br />Understanding bacteria<br />Sociomicrobiology<br />The “new” science of<br />Tools for synthetic biology<br />Microbes do have social life and well adopted Why do we work on it?<br />Dr.T.V.Rao MD<br />8<br />
In the past decade, significant debate has surrounded the relative contributions of genetic determinants versus environmental conditions to certain types of human behavior<br />Genetics x environment <br />Dr.T.V.Rao MD<br />9<br />
A structured community of bacterial cells enclosed in a self-produced polymeric matrix.<br />-Biofilms are a protective mode of growth that allows survival in hostile environments.<br />-Bacteria in biofilms are inherently resistant to killing.<br />What is a Biofilm?<br />Dr.T.V.Rao MD<br />10<br />
Biofilms are …….<br />Biofilms are multicellular aggregates of bacteria and yeast that congregate on surfaces.<br />Biofilm may form on any surface exposed to biofilm-forming bacteria and some amount of water. <br />Biofilms are formed to protect the bacteria from host defenses, antibiotics, and from harsh environmental conditions.<br />Dr.T.V.Rao MD<br />11<br />
Biofilms are communities of Microorganisms <br />Biofilms are communities of microorganisms that develop on surfaces in most natural and artificial environments. Biofilm maturation requires cell contact with a surface and cell-cell adhesion counteracting the shear forces of the environment. Biofilms are characterized by a surface covered by a high number of cells (a film) encased in a self-produced extra cellular matrix, are highly heterogeneous environment, both at structural, physiological and specific levels and biofilm bacteria express still under-explored specific biological properties such as a characteristic increased tolerance to biocides<br />Dr.T.V.Rao MD<br />12<br />
Biofilms are found almost everywhere in nature, including rivers, lakes, soil, water pipes, and even inside the human body<br />Bacterial biofilms are often a cause of infections associated with medical implants such as catheters and IV lines and other medical devices. <br />Where are Biofilms Found?<br />Dr.T.V.Rao MD<br />13<br />
Biofilms are concern in every aspect of life<br />Dr.T.V.Rao MD<br />14<br />
The Dynamics of Growing Biofilm <br />Quorum Sensing:<br />What is it?<br />How does it work?<br />Heterogeneous structures:<br />How do these cells use polymer gel for locomotion?<br />What are the mechanisms of pattern (structure) formation?<br />Why is polymer gel so effective as a protective environment?<br />Dr.T.V.Rao MD<br />15<br />
Biofilms are important survival mechanisms for bacterial cells. According to in vitro studies, they can avoid attack by host defenses. it is difficult for phagocytic cells to engulf bacteria in biofilms. Also, biofilms are much more resistant than planktonic cells to antimicrobial agents. The bacteria within the biofilm remain healthy, and the biofilm can regrow. Repeated use of antimicrobial agents on biofilms can cause bacteria within the biofilm to develop an increased resistance to biocides.<br />Biofilms are advantageous to microorganisms<br />Dr.T.V.Rao MD<br />16<br />
In medicine, biofilms spreading along implanted tubes or wires can lead to pernicious infections in patients. Biofilms on floors and counters can make sanitation difficult in food preparation areas.<br />Dental plaque is a yellowish biofilm that build up on the teeth. If not removed regularly, it can lead to dental caries.<br />Biofilms in medicine<br />Dr.T.V.Rao MD<br />17<br />
Why Research on Biofilms?<br />Due to the morphology of biofilms, bacteria capable of forming them are highly resistant to antibiotics, making treatment very difficult. <br />In the US alone, one million nosocomial (hospital acquired) infections each year are caused by bacterial biofilms, leading to longer hospitalization, surgery, and even death.<br />Dr.T.V.Rao MD<br />18<br />
Biofilms and Infections:<br />Biofilms are responsible for Otitis Media, the most common acute ear infection.<br />Biofilms play a role in Bacterial Endocarditis (infection of the inner surface of the heart and its valves). <br />Biofilms form frequently in patients with Cystic Fibrosis (a chronic disorder resulting in increased susceptibility to serious lung infections). <br />Biofilms also play a role in Legionnaire's disease (an acute respiratory infection resulting from the aspiration of clumps of Legionnella biofilms detached from air and water heating/cooling and distribution systems).<br />Dr.T.V.Rao MD<br />19<br />
A process that enables bacteria to communicate using secreted signaling molecules called auto inducers<br />This process enables a population of bacteria to regulate gene expression collectively and therefore, control behavior on a community-wide scale.<br />Quorum Sensing<br />Henke and Bassler, 2004<br />Dr.T.V.Rao MD<br />20<br />
Model of Chronic Pseudomonas aeruginosa<br />Infection in Cystic Fibrosis<br />Environmental Pseudomonas<br />Lung <br />Disease<br />Bacterial Adaptation <br /><ul><li> Alginate/mucoidy
How pathogenic Bacteria Use Quorum Sensing<br />These changes culminate in an infection that can ambush and overwhelm our immune system defenses. <br />The bacteria appear relatively innocuous as they quietly grow in number.<br />When their population reaches a certain level, instant changes occur in their<br /><ul><li> Behavior
Quorum Sensing Systems: Gram negative bacteria<br />Lux I/R systems<br />Auto inducers: acylated homoserine lactone<br />Lux I-type enzymes synthesize acylated homoserine lactone (AHL) auto inducers by ligating a specific acyl moiety to the homocysteine moiety of S-adenosylmethionine (SAM)<br />LuxR-type proteins bind their cognate autoinducers and control transcription of target genes.<br />Dr.T.V.Rao MD<br />26<br />
Quorum Sensing Systems: Gram positive bacteria<br />Two-component systems involved<br />Autoinducers: modified oligopeptides<br />The signals are synthesized as precursor peptides, which are subsequently processed and secreted<br />Sensor histidine kinases detect the extracellular peptide autoinducers, autophosphorylate and transmit sensory information via phosphorylation of a response regulator<br />Response regulator changes gene expression<br />Dr.T.V.Rao MD<br />27<br />
The Chain of Command in Bacterial Communication<br />Dr.T.V.Rao MD<br />28<br />
Quorum Sensing in P. Aeruginosa<br />Quorum Sensing: The ability of a bacterial colony to sense its <br /> size and regulate its activity in response.<br />Examples:P. aeruginosa<br />P. Aeruginosa <br /><ul><li>Major cause of hospital infection in the US.
Major cause of deaths in intubated CF patients, and IV fed patients.</li></ul>P. Aeruginosa in planktonic (non-colonized) form are non-toxic, but <br />as a biofilm, they are highly toxic and well protected by the polymer <br />gel in which they reside. However, they do not become toxic or begin <br />to form polymer gel until the colony is of sufficient size to overwhelm <br />the immune system. Before this, they cannot be detected by<br />the immune system.<br />Dr.T.V.Rao MD<br />29<br />
Quorum sensing in P. Aeruginosa<br />Planktonic<br />Loosely Bound<br />EPS secreting<br />Dr.T.V.Rao MD<br />30<br />
“Wall Sensing” in P. Aeruginosa<br />Wall Sensing: The ability of bacteria to differentiate in response to<br />Contact with a wall (the substratum). <br />EPS secreting<br />Planktonic<br />Loosely Bound<br />Dr.T.V.Rao MD<br />31<br />
AHL type autoinducers are for intraspecies communications<br />AI-2 and its synthase, LuxS, are widespread, existing in many bacterial phyla. AI-2 is suggested to serve as an interspecies bacterial communication signal.<br />Intraspecies vs. interspecies communications<br />Dr.T.V.Rao MD<br />32<br />
How quorum sensing works?<br />Signaling compounds, auto inducers<br /> AI synthases (luxIgene products)<br /> cell density indicators <br /> - non-essential aa, acyl homoserine lactones <br /> lactone ring part - binding to a receptor site<br /> acyl chain tail – determining the species specificity <br /> - oligopeptides <br /> - diketopiperazines<br /> - quinolone<br /> - furanones <br />Recognition systems<br />LuxR transcriptional regulator<br /> specific binding sites for AHL and DNA (sensor/transducer)<br />Genetic basis<br /> regulatory circuit involving both regulatory genes <br /> accumulation of AHL - activating gene transcription<br />
Laboratory made molecules have solutions to counter quorum sensing<br />Autoinducer 2 may hold the key to disrupting quorum-sensing.<br />AI-2 contains the element boron<br />AI-2 and similar boron-containing molecules made in the laboratory could serve as decoys to subvert virulence and other quorum-sensing behaviors<br />Dr.T.V.Rao MD<br />34<br />
Communication Between Prokaryotes and Eukaryotes<br />Chemical communication extends to the eukaryotic hosts with which bacteria engage in pathogenic and symbiotic relationships.<br />P. aeruginosa AHLs enter eukaryotic cells and stimulate production of chemokine interleukin 8 (IL-8), which in turn induces the NF-kB transcription factor.<br />These responses cause recruitment of neutrophils to the lung, in which they contribute to pulmonary inflammation and tissue deterioration.<br />Dr.T.V.Rao MD<br />36<br />
37<br />Need for Inhibition of quorum sensing<br /><ul><li>Inhibition of quorum sensing has been proved to be very potent method </li></ul> for bacterial virulence inhibition.<br /><ul><li> Several QS inhibitors molecules has been discovered.
QS inhibitors have been synthesized and have been isolated from several </li></ul> natural extracts such as garlic extract.<br /><ul><li> QS inhibitors have shown to be potent virulence inhibitor both in in-vitro</li></ul> and in-vivo, using infection animal models.<br />
38<br />What is the need for Quorum sensing inhibitors ?<br />
39<br />Strategies for quorum sensing inhibition<br />3 strategies can be applied<br />Targeting AHL signal<br />dissemination<br />Targeting the signal <br />receptor<br />Targeting signal <br />generation<br />Signal precursor<br />Signal precursor<br />Signal precursor<br />X<br />Signal<br />Signal<br />Signal<br />X<br />X<br />Signal receptor<br />Signal receptor<br />Signal receptor<br />
Further studies are needed on quorum sensing<br />regulated gene expression<br />– Onset of QS<br />– Affects on Onset<br />• Architecture and physical flow<br />• Functional consequences on biofilm<br />community<br />• Role in mixed species systems<br />• Effects of signal consumption<br />Further research is needed in sociomicrobiology on ….<br />Dr.T.V.Rao MD<br />40<br />
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