The cell wall is the tough, flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, in addition to acting as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell. Cell walls are found in plants, bacteria, fungi, algae, and some archaea. Animals and protozoa do not have cell walls.
The material in the cell wall varies between species, and can also differ depending on cell type and developmental stage. In bacteria, peptidoglycan forms the cell wall. Archaean cell walls have various compositions, and may be formed of glycoprotein S-layers, pseudopeptidoglycan, or polysaccharides. Fungi possess cell walls made of the glucosamine polymer chitin, and algae typically possess walls made of glycoproteins and polysaccharides. Unusually, diatoms have a cell wall composed of biogenic silica. Often, other accessory molecules are found anchored to the cell wall.
Bacterial cellulose is an organic compound with the formula (C
n) produced from certain types of bacteria. While cellulose is a basic structural material of most plant substances, it is also produced by bacteria, principally of the genera Acetobacter, Sarcina ventriculi and Agro bacterium. Bacterial, or microbial, cellulose has different properties from plant cellulose and is characterized by high purity, strength, moldability and increased water holding ability. In natural habitats, the majority of bacteria synthesize extracellular polysaccharides, such as cellulose, which form protective envelopes around the cells. While bacterial cellulose is produced in nature, many methods are currently being investigated to enhance cellulose growth from cultures in laboratories as a large-scale process. By controlling synthesis methods, the resulting microbial cellulose can be tailored to have specific desirable properties. For example, attention has been given to the bacteria Acetobacter xylinum due to its cellulose’s unique mechanical properties and applications to biotechnology, microbiology, and materials science. Historically, bacterial cellulose has been limited to the manufacture of Nata de coco, an indigenous food of South-East Asia. With advances in the ability to synthesize and characterize bacterial cellulose, the material is being used for a wide variety of commercial applications including textiles, cosmetics, and food products, as well as medical applications. Many patents have been issued in microbial cellulose applications and several active areas of research are attempting to better characterize microbial cellulose and utilize it in new areas.
As a material, cellulose was first discovered in 1838 by Anselme Payen. Payen was able to isolate the cellulose from the other plant matter and chemically characterize it. In one of its first and most common industrial applications, cellulose from wood pulp was used to manufacture paper. It is ideal for displaying information in print form due to its high reflectivity, high contrast, low cost and flexibility. The discovery of cellulose produced by bacteria, specifically from the Acetobacter xylinum, was accredited to A.J. Brown in 1886 with the synthesis of an extracellular gelatinous mat. However, it was not until the 20th century that more intensive studies on bacterial cellulose were conducted. Several decades after the initial discovery of microbial cellulose, C.A. Browne studied the cellulose material obtained by fermentation of Louisiana sugar cane juice and affirmed the results by A.J. Brown. Other researchers reported the formation of cellulose by other various organisms such as the Acetobacter pasteurianum, Acetobacter rancens, Sarcina ventriculi, and Bacterium xylinoides. In 1931, Tarr and Hibbert published the first detailed study of the formation of bacterial cellulose by conducting a series of experiments to grow A. xylinum on culture mediums.
Hospitality is the relationship between the guest and the host, or the act or practice of being hospitable. This includes the reception and entertainment of guests, visitors, or strangers.