An Introduction to Molecular Biotechnology. Группа авторов

      In the meantime, several pathogenic bacteria (e.g. Pseudomonas aeruginosa and S. aureus) have become increasingly resistant to effective antibiotics, causing thousands of death. This is why the development and production of new antibiotics should remain a high priority for the biotechnological industry. Also the development, of reliable and fast analytical devices, is a relevant area of biotechnology.

      Organic low‐molecular‐weight compounds such as amino acids or recombinant proteins are often produced in bacteria (see Chapter 16). Sometimes, genetic manipulation of biosynthetic pathways can give a substantial boost to the yield (Chapter 31).

      The human body harbors trillions (around 10¹⁴ cells) of bacteria, fungi, and protozoa from thousands of species in the gastrointestinal tract but also on skin and epithelia of mouth and vagina. This community is termed microbiota and their genomes the microbiome. The composition of the microbiota of an individual is due to variation, depending on age, food, health, and antibiotic use. The organisms in the microbiota show many ecological relationships with the human host, ranging from mutualism, commensalism, and parasitism. Using next generation sequencing (NGS) it is presently possible in a single analysis to obtain an overview, which species are present in the microbiota of an individual and in which abundance. Apparently, the composition of the microbiota plays an important and beneficial role for the health of an individual. It will be a challenge to manipulate the microbiota of an individual using fecal transplants or the administration of “good” microorganisms.

3.3 Structure of Viruses

Viruses (or phages when found in bacteria) are not autonomous organisms. Although they have some cell elements in common with bacteria (DNA or RNA as genetic information) (Table 3.7), they depend on host cells for their propagation. They invade bacterial, plant, or animal host cells to live as parasites. Excessive viral multiplication causes the death of host cells and thus disease in the host. The way how a virus enters the body and how it establishes itself in cells is very intricate and differs between virus and cell type.

Table 3.7 Classification of major animal and human pathogenic viruses.

      Viral nucleic acid (Table 3.7) is enclosed by a protein envelope or capsid. Many viruses carry a biomembrane on the outside, which is derived from the host cell. It contains viral proteins (envelope proteins) that act as antigens. Viral proteins are often very variable. By modifying their surface antigen, whenever they multiply, they are able to outcompete the immune system, which cannot keep up the speed to produce the latest specific antibodies. Viral proteins are tailor‐made for each other. This enables them to spontaneously form supramolecular complexes and infectious viral particles.

Retroviruses, such as the HIV pathogen, are medically very significant (Table 3.7). They carry genetic information as RNA (Figures 1.3b and 3.28). The retroviral genome codes for a relatively low number of gene products, among others, for reverse transcriptase, which translates viral RNA into DNA (cDNA). Oncogenes have the ability to transform cells into tumor cells. The discovery of viral oncogenes was essential for the understanding of regulatory mechanisms that are involved in cell division, cell differentiation, and the development of cancer (Table 3.8).