In the natural universe, a broad assortment of micro-organisms exist within the dirts of the Earth. The types of life signifiers vary from Fungis to roundworms to protozoa to bacteriums. Each serve their ain intent in the environment, and contribute to the overall construction of the community ( Willey et al. 2008 ) .

The focal point of our experiments is on bacteriums. Like other micro-organisms, bacteriums play a critical function in their several communities, and have their ain specific demands. Bacterias are really diverse, and are classified into groups depending on their metamorphosis, morphology, and other features.

Depending on their O tolerance, they are separated into the groups of obligate aerobes, microaerophiles, obligate anaerobes, aerotolerant anaerobes, or facultative anaerobes. Cellular form and agreements are besides used to sort bacteriums. The sum of peptidoglycan doing up the cell wall of a bacteria can be used to find if a bacteria is gram negative or gram positive. Bacterias are farther classified by what food and energy beginnings they use, as heterotrophs or autophyte, every bit good as by their growing in changing environmental conditions, such as temperature and pH ( Willey et al. 2008 ) .

Bacterias have a cardinal function in the environment. They are really of import in the cycling of foods, and many bacteriums are a cardinal factor in the N rhythm through the procedures of nitrification and denitrification, and are besides of import in decomposition and digestion. However, bacteriums are besides used for other intents. These include things such as the usage of bacteriums for nutrient production, chemical production, pharmaceuticals, waste disposal, and pest control. Lastly, some bacteriums are pathogens, doing disease in both workss and animate beings ( Willey et al. 2008 ) .

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!

order now

The end of this experiment was to place the bacteriums collected from dirt samples, based on specific trials and observations.

Materials and Methods

The experiment was carried out as harmonizing to the Biology 203 Lab Manual. All single trial processs and reagents used can be found in the lab manual ( Robertson and Egger 2008 ) .

Two different samples incorporating the bacteriums were collected, and diluted to 10-9 to 10-2 samples. Using proper technique, assorted trial tubings and home bases were inoculated with the samples. These civilizations were incubated in aerophilic and anaerobiotic environments, and growing observations were made. The figure of settlement organizing units was so determined by numbering. Four distinguishable settlements were so selected, and settlement morphology was noted. These settlements were so sub-cultured, once more utilizing proper sterile technique. Using the microscope, measurings and observations were made. Gram discoloration trials were so performed on the subcultures. Next, amylum hydrolysis, S and motility, ammonification, nitrification, denitrification, and catalase presence were all tested for with their several trials and reagents, and observations were noted. Last, the bacteriums were incubated in changing temperatures, pH, and salt concentrations. Optimum temperature, pH, and osmotic force per unit area were noted for each of the bacteriums.




Colony Morphology

Circular, raised, smooth

Cell Morphology


Gram Stain


Starch Hydrolysis


H2S decrease







( NO3- to NO2- )



( NO3- to NH3 or N2 )



( NH3 / NH4+ to NO2- )



( NH3 / NH4+ to NO3- )




Optimum Temperature

22 Degrees Celsius

Optimal pH


Optimal Salt Concentration

2 %

Possible Identity?

Genus: Lactobacillus

Figure 1 aa‚¬ ” Observations for Unknown Bacteria

The bacterial settlement, after incubation, was found to be round, raised, glistening and opaque, with a smooth texture and black in colour. The cells of the settlement were observed to be rod molded ( B ) , and arranged in a remarkable form. The cell was about 7 um in diameter. The bacteria was besides found to be positive for gm staining. The bacteria was besides found to veto for any H2S decrease or motility as indicated by the SIM tubing. It was observed the unknown bacteria did non hydrolyse amylum. Using proper reagent trials, it was found that the bacteria did non undergo denitrification, but did undergo nitrification. The bacteria was besides found to be positive for catalase presence, bespeaking aerophilic respiration. Optimum growing conditions for the bacteria included a temperature of 22 grades Celsius, a pH of 5, and a salt concentration of 2 % .


From the consequences of our trials, every bit good as our observations, a possible genus for our unknown bacterium is Lactobacillus ( Bergey, S. 1984 ) . Bacteria from the lactobacillus genus are rod aa‚¬ ” shaped, and Gram-positive. They undergo nitrification, but do non undergo denitrification. Optimum growing conditions for lactobacillus include temperatures in the 22 grades Celsius scope, a somewhat acidic pH, and salt concentrations about 2 % . All of these factors correspond with the unknown bacterium. Besides, although many members of the lactobacillus genus trial negative for catalase presence, there are some that respire aerobically every bit good ( Bergey, S. 1984 ) . The unknown tested positive for catalase presence, bespeaking that it is either a facultative anaerobe or aerotolerant anaerobe. Lactobacilli that trial positive for catalase presence are normally classified as facultative anaerobes ( Willey et al. 2008 ) .

In nature, the genus lactobacillus is a big component of the lactic acid bacteriums group. The bacterium of this genus carry out homolactic agitation utilizing the Embden-Meyerhof tract or heterolactic agitation utilizing the pentose phosphate tract ( Willey et al. 2008 ) . By this agitation, the bacteriums convert lactose and other sugars to lactic acid, with lactic acid being the lone merchandise of the reaction ( Willey et al. 2008 ) . Members of the genus lactobacillus do the natural vegetation of the human organic structure, and many of them in countries such as the oral cavity and digestive piece of land ( Willey et al. 2008 ) . Although most members of this genus are harmless, some have been linked to dental cavities ( Nase et al. 2001 ) .

Lactobacillus is besides used to a great extent in nutrient production. Products that include the usage of lactobacilli include cheese, beer, vino, fermented vegetable nutrients, and yoghurt ( Willey et al. 2008 ) . Some lactobacilli, nevertheless, may supply unwanted consequences and spoil nutrients such as meat and milk due to their metabolic terminal merchandises ( Willey et al. 2008 ) . Some lactobacilli are besides used as probiotics that can supply wellness benefits such as protection from GI diseases ( Marteau et al. 2001 ) .

To farther assistance in designation of our bacteriums, more trials could hold been used, such as a saccharide agitation trial. With this trial, acid and/or gas would hold been produced during fermentative growing with sugar or sugar intoxicants. This would hold worked, because lactobacilli rely on sugar agitation for energy ( Willey et al. 2008 ) . Another trial that could hold been used is the cytochrome trial, which detects the presence of cytochrome hundred oxidase. Lactobacillus would hold tested negative for this, as they lack cytochromes because they obtain energy from substrate degree phosphorylation instead than oxidative phosphorylation ( Willey et al. 2008 ) . Restrictions of the trials that we performed include the fact that they were non specific plenty to to the full find the species of our unknown merchandise. Our trials provided merely a wide position.

Beginnings of mistake that may hold affected consequences include the possibility that we may non hold used proper sterile technique during an vaccination, and besides that some of our trials provided consequences that were non clear. For illustration, the gm staining trial did non supply wholly distinct consequences ; there was trouble in finding whether the trial was positive or negative. Besides, consequences for the ammonification trial were inconclusive.


I'm Niki!

Would you like to get a custom essay? How about receiving a customized one?

Check it out