One way of identifying and categorizing multiple bacterial organisms in a sample is to use ribotyping.  In ribotyping, differing lengths of chromosomal DNA are isolated from samples containing bacterial species, and digested into fragments.  Similar types of fragments from differing organisms are visualized and their lengths compared to each other by Southern blotting or by the much faster method of polymerase chain reaction (PCR) .  Fragments can then be matched with sequences found on bacterial species.  Ribotyping is shown to be a method to isolate bacteria capable of spoilage.  Around 51% of Pseudomonas bacteria found in dairy processing plants are P. fluorescens, with 69% of these isolates possessing proteases, lipases, and lecithinases which contribute to degradation of milk components and subsequent spoilage.  Other Pseudomonas species can possess any one of the proteases, lipases, or lecithinases, or none at all.  Similar enzymatic activity is performed by Pseudomonas of the same ribotype, with each ribotype showing various degrees of milk spoilage and effects on flavour.  The number of bacteria affects the intensity of spoilage, with non-enzymatic Pseudomonas species contributing to spoilage in high number. 
After Spain sent Columbus on his first voyage to the New World in 1492, other explorers followed. The first Europeans to arrive in territory of the modern United States were Spanish conquistadors such as Juan Ponce de León , who made his first visit to Florida in 1513; however, if unincorporated territories are accounted for, then credit would go to Christopher Columbus who landed in Puerto Rico on his 1493 voyage . Spanish set up the first settlements in Florida and New Mexico such as Saint Augustine  and Santa Fe . The French established their own as well along the Mississippi River . Successful English settlement on the eastern coast of North America began with the Virginia Colony in 1607 at Jamestown and the Pilgrims' Plymouth Colony in 1620. Many settlers were dissenting Christian groups who came seeking religious freedom . The continent's first elected legislative assembly, Virginia's House of Burgesses created in 1619, the Mayflower Compact , signed by the Pilgrims before disembarking, and the Fundamental Orders of Connecticut , established precedents for the pattern of representative self-government and constitutionalism that would develop throughout the American colonies.