Lecture #4: Last History, Gram Stain Flashcards
Molecular Advances
Microbes are model systems for learning about gene function and gene regulation.
Bacteria, viruses, and simple yeasts typically have smaller genomes;
- -fewer genes overall,
- -bacteria, viruses have little non-coding DNA.
- -in bacteria, genotype expressed directly. Haploid.
Plasmids
Small, double-stranded DNA molecules that can exist independently of the chromosome. Both circular and linear plasmids have been documented, but most known plasmids are circular. Plasmids have relatively few genes, generally less than 30. Their genetic info is not essential to the host, and cells that lack them usually function normally. However, many plasmids carry genes that confer a selective advantage to their hosts in certain environments.
Plasmids are able to replicate autonomously. That is, plasmid and chromosomal replication are independent. Single-copy plasmids produce only one copy per host cell. Multicopy plasmids may be present at concentrations of 40 or more per cell.
Plasmids are inherited stably during cell division, but sometimes go through curing.
Extra DNA not necessary to basic function.
Taken up from the surrounding media.
Introduce new capabilities. Vector to carry in new genes.
Can introduce genes from another cell of the same species, from a different microbe, or a wholly different organism (rDNA).
Recombinant DNA Has Brought Us
Drugs, vitamins, various chemicals (acetone, ethyl alcohol, hormones) produced in good quantity cheaply using bacteria equipped with a human gene.
Crop plants resistant to pests, pesticides or frosts. High lysine corn, enriched rice, and other produce enriched nutritionally.
Limited success with human gene therapy (cancer, leukemia).
Nucleic Acid Sequences Used to Determine Evolutionary Relatedness
DNA segments sequenced and the number of nucleotide changes provides an index to how closely related two organisms are, relative sense. Location of the change can provide a rough order (time sequence, phylogeny). Quick exercise.
Specific DNA probes can help identify particular organisms in a mixed sample, or locate similar sequences in different organisms. Quick exercise.
RNA gene sequences are used in establishing major groups.
Sergei Winogradsky
(1856-1953) Russian microbiologist. Made many contributions to soil microbiology. He discovered that soil bacteria could oxidize iron, sulfur, and ammonia to obtain energy and that many of these bacteria could incorporate CO2 into organic matter much as photosynthetic organisms do. Winogradsky also isolated anaerobic nitrogen fixing soil bacteria and studied the decomposition of cellulose.
Winogradsky
Developed by Sergei Winogradsky in the 1880’s.
Idea that bacteria live in natural communities based on needs and metabolic fortés (specialties).
Vary what you start with (chemicals, light, source of bacteria, source of foods…), get an interdependent functioning community—ultimate organisms and their abundance varies with the starting conditions.
Biofilms
Discovery that bacteria form interdependent communities in your body as well as in nature. Cells cooperate, communicate, and can launch attacks against their host. Resilient against harsh conditions such as antibiotic treatment.
Biofilms & Chronic Disease
Cells within a matrix of goo produced by all cells (common gene regulation). Matrix is protective, with reduced penetration of drugs.
Relates to chronic diseases and infections that are difficult to treat using antibiotics.
Human Microbiome
Humans have specialist bacteria (types, amounts) in different parts of their bodies.
Microbes contribute to health, and must be in the appropriate balance.
To restore a healthy balance in a diseased person, introduce the right types. Probiotics, bacterial transplants.
Pasteur & the Dirt Vaccine
Mice born and raised with other sibs – good vitality, good immunity.
Mice sterilized of bacteria at birth and raised in a sterile environment – poor vitality, extreme susceptibility, weak immunity.
Normal mice injected with: a pathogen. Died. a pathogen and then a dirt vaccine. Lived, good immunity.
Hygiene Hypothesis
Idea that exposure to microbes in dirt, from animals, and from family members is protective. Leads to calming of the immune system for certain microbes to which you are regularly exposed.
Daycare and stronger immunities.
Cholera
Cholera is a disease caused by a rod shaped bacterium (Vibrio cholerae).
In India, it causes serious health problems particularly in children aged 1-5. Vibrio contaminates the water supply and leads to malnutrition (dehydration, vomiting, diarrhea).
Rita Colman Offered Effective Solution
Tetracycline can resolve symptoms and start recovery, use must be on-going. Western drug-based cure. Most there could not afford the on-going drug therapy.
Pragmatic approach. Easy to do. Respectful of culture and of the poverty. Empowered the local people and spread quickly. In place, and widespread, today because of her sensitivity. Later in the hall…
Gram Positive Bacteria
Thick cell wall on the outside, and retain the Crystal Violet stain. End result = Purple.
Gram Negative Bacteria
Thin cell wall, located in a membrane sandwich (outer membrane, cell wall, cell membrane). CV stain washes out and cells show the second stain or counterstain (pink).
