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BACTERIA

BACTERIA. DR NAZIA KHAN ASSISTANT PROFESSOR COLLEGE OF MEDICINE. MORPHOLOGY AND PHYSIOLOGY OF BACTERIA. Belong to kingdom protista which is divided into prokaryotes and eukaryotes Differences between prokaryotes and eukaryotes. Bacteria are prokaryotes. MICROSCOPES. LIGHT MICROSCOPE

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BACTERIA

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  1. BACTERIA DR NAZIA KHAN ASSISTANT PROFESSOR COLLEGE OF MEDICINE

  2. MORPHOLOGY AND PHYSIOLOGY OF BACTERIA • Belong to kingdom protista which is divided into prokaryotes and eukaryotes • Differences between prokaryotes and eukaryotes

  3. Bacteria are prokaryotes

  4. MICROSCOPES • LIGHT MICROSCOPE • BRIGHT FIELD MICROSCOPE • PHASE CONTRAST MICROSCOE • DARK FIELD MICROSCOPE • FLUORESCENCE MICROSCOPE • DIFFERENTIAL INTERFERENCE CONTRAST (DIC) MICROSCOPE • ELECTRON MICROSCOPE • CONFOCAL SCANNING LASER MICROSCOPE

  5. STAINED PREPRATIONS • Live bacteria do not show much structural detail under light microscope due to lack of contrast, hence it is necessary to use staining techniques to produce colour contrast. Examples are: • Simple stains eg: Methylene blue • Negative stains eg: india ink • Impregnation methods: eg: spirochetes • Differential stains: Grams stain Z.N stain

  6. SHAPE OF BACTERIA • COCCI • BACILLI • VIBRIOS • SPIRILLA • SPIROCHETES • ACTINOMYCES • MYCOPLASMA

  7. BACTERIAL ANATOMY

  8. Cell wall may be gram negative or gram positive A

  9. GROWTH AND MULTIPLICATION OF BACTERIA • Bacteria divide by binary fission • When a bacterial cell reaches a certain size,it divides to form two daughter cells

  10. BACTERIAL NUTRITION • The principle constituent of bacterial cell is water, ,proteins,polysaccharide, , lipids, nucleic acids, mucopeptides, and low molecular weight compounds make up the rest.

  11. Culture media • Bacteria have to be grown (cultured) for them to be identified,as only rarely can they be recognised by their morphology alone. • The original media was used by Louis Pasteur • Types of media • Culture media may be liquid or solid or semisolid • Simple,complex, synthetic, special media may be enriched,enrichment,selective, indicator,transport • Aerobic and anaerobic

  12. CULTURE METHODS • The indications for culture are • Isolate bacteria in pure culture • Demonstrate their properties • Obtain growth for preparation of antigens and for other tests • Type isolates by methods such as bacteriophages • Determine sensitivity to abtibiotics • Maintain stock cultures

  13. Anaerobic culture methods • Cultivation in vaccum • Displacement of oxygen with gases such as hydrogen,nitrogen,helium or carbon dioxide Eg: Candle jar 3. Pyrogallol 4. Mc intoshfielde’s Jar 5. Reduction of oxygen in the medium is achieved by the use of various reducing agents, including 1% glucose, 0.1% thioglycollatte, ,0.1% ascorbic acid 6. Robertsons’s cooked meat medium

  14. Identification of bacteria • Morphology • Staining reactions • Culture • Biochemicals • Serology • Antimicrobial susceptibility testing

  15. Examples of bacteria Gram positive Gram negative Cocci . Bacilli Nisseria 1.Escherichia • Cocci .Bacilli • Staphylococcus 1. Bacillus • Streptococcus 2.Corynbacterium

  16. BACTERIAL GENETICS

  17. GENETICS • PROCESS OF HEREDITY AND VARIATION • THE ABILITY OF A MICROORGANISM TO MAINTAIN VIABILITY,ADAPT,MULTIPLY,AND CAUSE DISEASE . • The science of genetics defines and analyzes heredity, or constancy and change in the vast array of physiologic functions that form the properties of organisms.

  18. TERMINOLOGY IN GENETICS

  19. . • GENE-segment of DNA that carries in its nucleotide sequence information for a specific biochemical or physiologic properties. It is the Unit of heredity • LOCUS-Large number of genes constitute locus • GENOME-All genes taken together within an organism comprise that organism’s genome.The size of gene and an entire genome is usually expressed in the number of base pairs(bp) present. Eg; kilobases ,megabases.

  20. . • BASE SEQUENCE-DNA and RNA are nucleotide polymers(i:e chains of strands) and the order of bases along a DNA or RNA strand is k/a base sequence. • GENETIC CODE-This sequence provides the information that specifies the proteins that will be synthesized by microbial cells(i:e the sequence is genetic code) • Genetic information is stored in DNA as a CODE and the unit of code is k/a CODON. • Code is -triplet -specific -degenerate/redundant -universal -non overlapping • There are 64 different codons for 20 amino acids. • NONSENSE/STOP CODONS-UAA,UAG,UGAdon’t code for any amino acid rather they terminate the message for the synthesis of polypeptide.

  21. . PHENOTYPE GENOTYPE a)Alteration in the sequence of DNA within a gene or in the organization of genes b)Not Influenced by environmental changes c)Are stable d)Heritable Genotypic variations are due to mutations or by other methods of genetic transfer a)Collective structural and physiologic properties of a cell or an organism b)Influenced by environmental changes c)Are temporary d)Not heritable Eg of phenotypic variation: typhoid bacilli

  22. CHROMOSOME The genome is organized into discrete elements known as chromosomes. • The set of genes in a given chromosome is arranged in a linear fashion, but the no. of genes per chromosome is variable. • Human cells contain 23 pair(diploid)of chromosome. Bacterial cell contains a single(haploid)chromosome. Bacterial chromosome: • Exists as ds,closed circular, naked macromolecule, folded and twisted i:e super coiled. • FOR GENES TO BE EXPRESSED AND REPLICATED,UNWINDING IS ESSENTIAL

  23. . .

  24. NONCHROMOSOMAL ELEMENTS OF GENOME PLASMIDS • Small extra chromosomal piece of genetic material that can replicate autonomously and can maintain in cytoplasm of bacterium for many generations. • Not essential for normal life • Confers-drug resistance ,bacteriocin production, toxigenecity • Not as stable as chromosome and may be lost during replication • TYPES:CONJUGATIVE & :NON CONJUGATIVE TRANSPOSABLE ELEMENTS • These are pieces of DNA that move from one genetic element to another, from plasmid to chromosome or vice versa. • Like plasmids they do not exist as free entities but they must either be incorporated into a plasmid or chromosome. • Also known as jumping genes • TYPES:INSERTION SEQUENCE : TRANSPOSONS EPISOME: If plasmid integrates into host cell genome. F-PLASMID: Confers maleness to host cell

  25. Structure and organization of genetic material. DEOXYNUCLEIC ACID(DNA) • Watson and crick - Structure of DNA . • AVERY, Mac LEOD,Mc CARTEY - DNA is the carrier of GENETIC INFORMATION. • . • Orientation of 2 DNA strands is described as antiparallel,one strand in 5’3’ while the complementary strand runs in 3’5’ direction • The complementarity of the bases enables one strand(TEMPLATE STRAND)to provide the information for copying or expression of information in the other strand(CODING STRAND). Each helical turn of the helix has one major groove and one minor groove. Many proteins with the capacity to bind DNA and regulate gene expression interact predominately with the major groove where atoms comprising the bases are more exposed.

  26. . Purine and pyrimidine + ribose or deoxyribose bases Nucleoside/deoxyribonucleoside + phosphoric acid Nucleotide or deoxynucleotide NUCLEIC ACID(DNA or RNA)

  27. . GENE EXCHANGE BETWEEN BACTERIA: • The three mechanisms by which bacteria physically exchange DNA include : • TRANSFORMATION • TRANSDUCTION • LYSOGENIC CONVERSION • CONJUGATION

  28. . MUTATIONAL DRUG RESISTANCE PLASMID-MADIATED DRUG RESISTANCE Due to development of degrading enzymes. Involves many drugs at one time. Degree of resistance is usually high. Can not be prevented by drug combinations. transferable. Metabolically normal. Virulence usually not decreased. • Due to decreased permeability to drug. • Involves resistance to one drug at one time. • Degree of resistance is usually low, infection can be treated by giving higher doses of antibiotic • Development of drug resistance can be prevented by treatment with drug combinations. • Resistance is not transferable to other organisms. • Resistant mutants are metabolically active. • Virulence of resistant mutants can be lowered.

  29. . GENETIC RECOMBINATION: • It is one of the major means by which bacteria may achieve genetic diversity and change. • In this process, some segment of DNA that originated from one bacterial cell(i:e donor) enters a second bacterial cell(i:e recipient) and is exchanged with a DNA segment of the recipient’s genome. • This is also referred to as HOMOLOGOUS RCOMBINATION because the pieces of DNA that are exchanged usually have extensive homology or similarities in their nucleotide sequences.

  30. . MEDICAL APPLICATIONS OF GENETIC ENGINEERING: • Production of medically useful proteins such as somatostatin, insulin,human growth hormone and some interferones is of great practical importance. • Interleukin-2 and blood-clotting factor VIII have recently been cloned. • An interesting development is the use of transgenic corn and soyabean plants to produce monoclonal antibodies for medical use. • Synthetic vaccines(for malaria and rabies) are also being tried. • DNA probes can be used for diagnosis of infections • A type of genetic surgery known as SOMATIC CELL GENE THERAPY may be possible.

  31. THANK YOU

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