The Effects of Environmental Factors on the Absorbance of Escherichia Coli

(Biology Dept.). 0.1 ml of E.coli K or 0.1ml of E.coli B was added to the 10 fold dilution. Using soft agar technique, the growth media mixture with E.coli was plated and incubated.

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.

Bacteria are small, unicellular prokaryotic microbes. They have many morphologies, which include rod-shaped, spherical, spirals, helices, stars, cubes, and clubs. Classification of bacteria begins with either aerobic (requiring diatomic oxygen for growth) or anaerobic (not requiring O2 for growth). Bacteria can simply be narrowed down to gram positive (organism that stains purple or blue by Gram stain) or gram negative (organism that stains red or pink by Gram stain). Many physical and nutritional factors influence bacterial growth. Physical factors include temperature (psychrophiles, thermophiles, and mesophiles), pH (neutrophiles, acidophiles, and alkalinophiles), O2 concentration (aerobic

On August 19th, 2015 this experiment was performed, by 6 separate lab groups.The experiment began by measuring 1 Ml of E. coli into a pipette and pump, then placing the bacteria into a culture medium. The E. coli and medium were then swirled together for a period of 15 minutes, until completely mixed. This mixture was then poured into a petri dish and allowed to solidify for 45 minutes. After the 45 minute solidification time, 5 small paper disks were inserted into the dish. 4 of the disk contained treatments of antibiotic and 1 was left untreated. The

These resources can be provided from the intestinal tract such as from the chyme. If these growth factors are provided to the bacteria, the colony can divide, reproduce and double in size every twenty (20) minutes. The colon is for the most part is an anaerobic environment. This is not a problem for Escherichia Coli. They are considered a facultative aerobe which allows them to grow in areas with or without oxygen. E. coli can exist in open environments as well, such as water, manure and soil. The availability of carbon substrates is one of the main critical factors and will depend on local conditions of the habitat. Temperature is often a factor in open environments. The unpredictability and fluctuating temperature can have a tremendous impact on E. Coil’s survival in open environments. pH levels of the soil and in particular soil acidity levels also will impact survival. (Manning,

A few different factors that affect bacterial growth are the availability of resources and nutrients, temperature and pH. (Act For Libraries) stated in the above paragraph, once the resources and nutrients are

Escherichia coli, commonly known as E. coli, is a bacteria. Though most types of E. coli are not harmful, there are certain pathogenic varieties. In shape, E. coli is a rod shaped (bacilli,) and about 1-2 micrometers in size. On the outer membrane, they have flagellum which they use for movement, and fimbria. Fimbria is slightly shorter than flagellum and is known as the “attachment pill,” as it is what the bacterium uses to attach to the host organism, in this case mostly the inside of an organism’s intestines. On the inside, E. coli has cytoplasm and DNA.

Broth is a nutrient-infused liquid medium used for growing bacteria. According to the result, the broth has turned cloudy. It shows that there are presences of E. coli and Klebsiella in the broth separately. When E.coli and Klebsiella are grown in broths separately, they may exhibit patterns of growth ranging from sediment at the bottom of the tube and turbid growth throughout the tube (Cultural Characteristics: Growth on Slants and Broths). Their cultural characteristic is classified as settled-diffuse. Nutrient broth is not a selective medium so that bacteria can survive in it even at the bottom of broth tube which has lowest oxygen percentage.

showed that the rate of the growth of bacteria increased with the increase in the incubation period, the

The results of the growth showed that E. coli had similar growth curves among the garlic extract dilutions as seen Figure 1A. The exponential growth rate constant showed a trend of having an increase in garlic extract would show an increase in the growth rate as seen in Table 2B. The growth rate constants were calculated with the growth curve equation with the

Another concept is ‘thermal death time’ which is the minimum time it takes for bacteria to be killed under a specific temperature. The final concept is ‘decimal reduction time’ which is the bacteria’s heat resistant level (Tortora, Funke & Case, 2015). A heat resistant level for a bacteria determines the specific amount of time that is takes for at least 90% of the bacteria to be killed. Among each concept all conclude in the bacteria being killed although as the bacteria is killed each concept determines in which way the bacteria will be killed.

On Plate I (LB) and Plate II (LB + Ampicilin), E.coli growth was expected to occur. Since the environment was not selective in Plate I, growth was expected to be found as lawn. This prediction was confirmed by the experiment. On Plate II, it was expected that either lawn or colonies would be found. The observed growth occured as lawn. On Plate III (YPD) growth was predicted, given the presence of all the nutrients that the auxotrophic yeasts cannot synthetize. Due to the usual non-selectivity of the medium, lawn was the expected type of growth. However, growth actually manifested as red colonies, an occurrence which will be explained in the Discussion section. On Plate IV (YNB, -AA) and Plate V (YNB, -AA, +5% AS) no growth was expected to happen given the absence of amino acids, which the auxotrophic yeast could not synthetize. The results were as predicted. On Plate VI (YNB, +AA-Arg, -AS ), it was expected to obtain colonies, due to the selectivity of the environment. This indeed was observed, in the form of white colonies.

In this lab experiment, students had to create a growth curve for E. coli. The E. coli growth curve would illustrate the progression of the population of E. coli a set time period. In this case, the growth curve depicted the population of E. coli over a 12-hour period. The growth curve for E. coli was created from the absorbance levels, the optical density(OD), recorded from the spectrophotometer.

The purpose of the two experiments was to determine the fundamental effects that temperature has on the growth and survival of bacteria. During the first experiment five different bacterial broth cultures of Escherichia coli, Pseudomonas fluorescens, Enterococcus faecalis, Bacillus subtilis and Bacillus stearothermophilus were individually incubated at temperatures of 5, 25, 37, 45 and 55°C for one week in an aim to distinguish the effect temperature has on growth and survival of the five different species. After one week they were observed for distinguishable changes by the turbidity showing an indication of bacterial growth, or the clarity an indication of no survival.

E. coli, M. luteus, and B. stearothermophilus samples were aseptically inoculated into five separate TSA plates each. After all plates were properly sealed with parafilm, one culture of each organism was incubated at a specific temperature (4˚C, 25˚C, 35˚C, 55˚C, or 70˚C) for 48 hours. The recordings made thereafter concerned each organism at each temperature, in observance of either presence or absence of growth.