1.2.1 Spectral modulation using site-directed mutagenesis
Spectral tuning through the use of random PCR mutagenesis has been previously attempted (Kim et al. 2008). From the mutants obtained, 8 showed red-shifted absorption maxima and 12 mutants are blue-shifted compared to the wild-type (Kim et al. 2008). However, most of these mutants showed a loss of pumping activity.Various other red-shifted mutants of PR and GR have been generated (Martin K.M. Engqvist, 2015) (Srividya Ganapathy, 2015). The most conventional method of generating retinal binding pocket mutants employs mismatch PCR. In the study by Ganapathy et. al, a red-shifted double mutant PR-D212N/F234S(PR-DNFS) was produced and tested with several retinal analogs for the
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al. 2015) since retinal binding and functional group interaction is delicate and may vary with protein mutations.
In the current study, we aimed to develop a directed evolution assay, which would allow us to generate and select mutants with red-shifted absorbance and conserved proton pumping ability simultaneously, using E. coli as a host organism. The main step in designing a directed evolution system in E. coli warrants a short overview of the relevant characteristics of the bacteria, which can be affected by a PR-generated light-driven PMF, and used for selection.
Previous studies have shown that PRs can provide a selective advantage to E. coli only under conditions of starvation or respiratory stress. When inhibited by depleting oxygen or by the respiratory poison azide, E. coli cells expressing proteorhodopsin are shown to become light-powered in a sense that illumination of the cells with green light creates a proton motive force capable of driving the flagellar motor (Walter et al. 2007) (Murray J. Tipping, 2013). This yields motile bacteria under respiratory stress where they would otherwise remain stagnant (Walter et al. 2007). Azide inhibits cytochrome oxidase and, thus, proton extrusion by the respiratory chain, stopping the flagellar motor (Gabel and Berg 2003).
In this research, we used sodium azide as a respiratory inhibitor of E. coli.
This pBlu lab had for purpose to present the changes of the strain of E. coli bacteria due to new genetic information being introduced into the cell. In this experiment we are freezing and heat shocking the E. Coli bacteria that is then forced to take the plasmid DNA. The E. coli then transforms the pBLu plasmid, which carries the genes coding for two identifiable phenotypes. After following the Carolina Biological steps our lab worked well and we able to see some colonies of bacteria on the plates. The x-gal plate showed a significant amount of bacteria to confirm that the pBlu plasmid took over the E. coli strain.
In this lab, the organism that we have been working with is the bacterium, Serratia marcescens. S. marcescens is a member of the Enterobacteriaceae family, and tends to grow in damp environments. S. marcescens is an ideal bacterium to work with in the lab because it reproduces quicker than other bacterium. This bacterium produces a special pigment called prodigiosin, which is red in color. The prodigiosin pigment is intensified when S. marcescens is grown at higher densities. During our experiment, temperature, pH, salinity concentration and oxygen requirements were tested on S. marcescens to measure their optimal growth and prodigiosin production.
The pGLO plasmid is engineered to express green fluorescent protein (GFP) in the presence of the sugar arabinose as well as the ampicillin resistance gene β-lactamase (bla) (Brown, 2011). Original E. coli HB101 do not have ampicillin resistance or the GFP gene allowing them to glow under UV light. In this experiment, we transformed E. coli HB101 with the pGLO plasmid by heat shock to make the bacterial cells competent, allowing the plasmid to enter the cell (Brown, 2011). The mixture of bacteria with pGLO plasmid were given recovery time after heat shock, then spread on LB/amp and LB/amp/ara agar plates. The bacteria mixture with no plasmid added were spread on LB and LB/amp agar plates and all four plates were incubated at 37°C for
The purpose of the PGLO lab was to be able to perform a procedure known as a genetic transformation. We used a procedure to transform bacteria with the gene that codes for a Green Fluorescent Protein (GFP). The actual source of the GFP gene that we used in this complicated experiment is the bioluminescent jellyfish Aequorea victoria. This protein causes the jellyfish to glow under a UV light that was provided in the dark. After the transformation procedure, the bacteria showed their newly acquired gene from a jellyfish and produced the fluorescent protein, which as a result, causes it to glow. If the bacteria glowed in the dark, that was the initial sign that the experiment was successful.
This experiment was designed to test and observe the transformation efficacy of the pUC18 and lux plasmids in making E. coli resistant to ampicillin. Both plasmids code for ampicillin resistance, however, the lux plasmid codes for a bioluminescence gene that is expressed if properly introduced into the bacteria’s genome. The E. coli cultures were mixed with a calcium chloride solution and then heat shocked, allowing the plasmids to enter the bacteria and assimilate into the bacterial DNA. The plasmids and the bacteria were then mixed in different test tubes and then evenly spread onto petri dishes using a bacterial spreader, heating the spreader between each sample to make sure there is no cross contamination. Each of the dishes was labeled and then incubated for a period of 24 hours. The results were rather odd because every single one of the samples grew. Several errors could have occurred here, cross contamination or possibly an error in preparation as every single sample in the class grew, meaning all samples of the bacteria transformed and became ampicillin resistant.
70µL of competent E.coli are added to both test tubes; pUC18 and Lux (Alberte et al., 2012). Both test tubes are then tapped and placed back into the ice bath for 15 minutes. While waiting, another test tube is obtained, filled with 35µL of competent cells and labeled NP for no plasmid. A water bath is preheated to 37 degrees Celsius and all three labeled test tubes are inserted into the bath for five minutes (Alberte et al., 2012). Using a sterile pipet 300µL of nutrient broth are inserted into both the control and Lux test tubes and 150µL are inserted to the no plasmid test tube to increase bacterial growth. All three test tubes are then incubated at 37 degrees for 45 minutes. Six agar plates are obtained and labeled to correspond each test tube, three of the plates contain ampicillin. A pipet is used to remove 130µl from each test tube containing a plasmid and insert it into the corresponding agar plate. For this, a cell spreader is first
The plasmid pGLO contains an antibiotic-resistance gene, ampR, and the GFP gene is regulated by the control region of the ara operon. Ampicillin is an antibiotic that kills E. coli, so if E. coli, so if E. coli cells contain the ampicillin-resistance gene, the cells can survive exposure to ampicillin since the ampicillin-resistance gene encodes an enzyme that inactivates the antibiotic. Thus, transformed E. coli cells containing ampicillin-resistance plasmids can easily be selected simply growing the bacteria in the presence of ampicillin-only the transformed cells survive. The ara control region regulates GFP expression by the addition of arabinose, so the GFP gene can be turned on and
After a retinal molecule absorbs light, the normally 11-cis form of the bound retinal molecule straightens to become the 11-trans from. This change activated the opsin molecule. Opsin activates transducin which is a G protein. This G protein then activates phosphodiesterase. Phosphodiesterase is an enzyme that breaks down cyclic-GMP. The break-down of cyclic-GMP removes them from the gated sodium channels and makes the gated sodium channels inactive. Because of this, sodium ion entry into the cytoplasm decreases.
In the pGLO Bacterial Transformation lab, Escherichia coli is transformed with a gene encoding green fluorescent protein by inserting a plasmid containing the GFP gene, beta-lactamase, and arabinose into the bacterium. Successfully transformed bacteria will grow in the presence of ampicillin and glow a bright green color under ultraviolet light. The sugar arabinose is responsible for switching on the GFP gene in the transformed cells, without it, the gene will not be expressed.
“While motility is commonplace among the prokaryotes, it is important to note the variety of structures responsible for motility. These structures vary depending not only on the organism in question, but also on the particular environment” (Bardy, Ng, & Jarrell, 2003). “Study of the bacterial flagellum has provided insights into many aspects of prokaryotic cellular activities including genetics and regulation, physiology, environmental sensing, protein secretion and assembly of complex structures” (Bardy, Ng, & Jarrell, 2003). “Continued study of all prokaryotic motility structures will provide knowledge that is likely to reach far beyond the topic of motility and pathogenicity” (Bardy, Ng,
The goal of this experiment was to investigate genetic transformation of E.coli through the reaction of organism to the vector pGLO plasmid. As mentioned, the pGLO plasmid contains genes coding for resistance to ampicillin (amp), and genes coding for production of the green fluorescent protein (GFP) which glows under UV light in the presence of arabinose (ara),which serves as a reporter gene. This green fluorescent
Retinitis pigmentosa is a group of inheritable diseases that is characterized by gradual deterioration of the photoreceptors in the retina. The photoreceptor cells in the retina, rod cells, are light sensitive cells that are able to sense low levels of light. The frequency of retinitis pigmentosa is one in four thousand births (Deng et al., 2015; Fahim et al., 2012; Haddad et al., 2016; Shu et al., 2012) People affected by retinitis pigmentosa will typically exhibit symptoms of night-blindness first, and this will precede a loss in the patient’s visual acuity field that starts from the outer edge and gradually moves inward resulting in a much smaller visual field and loss of peripheral vision, also known as tunnel vision (Haddad et al., 2016).
In our hypothesis we stated that only the container containing all of the components +pGLO, LB broth, ampicillin, and arabinose would be the one that genetically transformed. In order for the bacteria to grow at a rapid pace all it needed was LB broth but when you added ampicillin, an antibiotic, it killed off all of the bacteria. +pGLO has the gene to resist the antibiotic so when that was added it was allowed to grow but there was no sugar to turn on the glowing protein. Finally, after arabinose, a sugar, was added it turned on the switch located in the +pGLO for the fluorescence and enabled to grow and glow.
In this lab, we demonstrated that a plasmid could be inserted into the DNA of bacteria in order to alter the physical characteristics of the bacteria. We used biotechnology to manipulate the genetic code of the bacteria so that it would glow when exposed to a UV light. After a couple of days when the glow of the bacteria started to fade, it became apparent that the operon system that enabled the pGLO gene to take affect was stopping.
This experiment was performed to test the hypothesis if LB nutrient broth, +pGLO and -pGLO Ampicillin, and Arabinose was placed in the E. coli plates, then there will be a significant growth in the newly transformed bacteria and it will possess the ability to glow under UV light. The measurements were recorded from the bent glass tube in each glass test tube. The transformation protocol tested for the newly possessed traits in E.coli bacteria. Throughout the experiment there were many probable reasons for failure. If the pipettes and sterile loop were not thrown out in between each use, a cross contamination could cause a miscalculation in the experiment causing the data results to fail. The hypothesis that was tested was validated due to the positive results with each experiment stating that newly transformed organisms due in fact pass on traits.