OLEH SUDRAJAT FMIPA UNMUL 2009
Struktur Sel Bakteri
Genom: Kandungan genetik total pada set haploid kromosom pada eukariot Kromosom tunggal pada bakteri atau pada DNA atau RNA virus Material genetik pada organisme
Genom bakteri terdiri dari kromosom sirkular Terkondensasi dengan cara supercoiling dan looping membentuk badan nukleoid yang tersusun secara rapat Kromosom bereplikasi di dalam sel dan sel membelah secara biner
Plasmids Extra chromosomal circular DNAs Ditemukan pada bakteri Ukuran bervariasi dari ~ 3,000 bp sampai 100,000 bp. Bereplikasi secara otonomi (origin of replication) Dapat mengandung gen resisten Dapat ditransfer dari satu bakteri ke bakteri lainnya Dapat ditransfer kepada kingdom yang berbeda Multicopy plasmids (~ up to 400 plasmids/per cell) Low copy plasmids (1 –2 copies per cell) Digunakan sebagai vektor untuk membawa gen yang diinginkan
7 CYTOPLASMIC STRUCTURES Nucleoid area of concentrated DNA no nuclear membrane The DNA is single circular double stranded without proteins
8 STRUKTUR SITOPLASMATIK Ribosom sitoplasmatik, bukan attached to organela Plasmid Extrachromosomal loops of DNA some code for drug resistance toxins
Genotypic Characteristics for Identifying Prokaryotes the use of genotypic testing has increased with the availability of technology genotypic testing is particularly useful in the case of organisms that are difficult to identify several techniques include gene probes PCR sequencing rRNA
Genotypic Characteristics for Identifying Prokaryotes gene probes single stranded DNA that has been labeled with a identifiable tag, such as a fluorescent dye are complementary to target nucleotide sequences unique in DNA of pathogen Microbe gene probed
Genotypic Characteristics for Identifying Prokaryotes If there is a suspicion, based on symptoms or other environmental parameters that indicates that the organism to be identified may be “ organism A”, a single strand of “organism A’s” DNA is introduced with a tag attached (such as fluorescent dye). If the introduced DNA binds to the unknown organism, then it is identified as “organism A”. If it does not bind to the unknown organism, then the unknown is not “organism A”.
Genotypic Characteristics for Identifying Prokaryotes PCR: polymerase chain reaction used to detect small amounts of DNA present in a sample (blood, food, soil) the PCR chain reaction is used to amplify the amount of DNA present
Genotypic Characteristics for Identifying Prokaryotes sequencing ribosomal RNA of particular use for identifying prokaryotes impossible to grow in a culture focus is place on the 16S molecules of the RNA because of it’s size approximately 1500 nucleotides once the 16S molecule is sequenced, it can then be compared to the sequences of known organisms Machine used to pick colonies containing wanted DNA
Difficulties in Classifying Prokaryotes historically prokaryotes have been grouped according to phenotypic attributes problems with this approach include mutation resulting in phenotypic changes “just because they look alike, does not mean that they are even closely related according the prokaryotics” new molecular approaches are providing better insight to the relatedness of microorganisms the more similar the nucleotide sequence, the more closely related DNA extraction
Genotypic Characteristics used in Classifying Prokaryotes comparison of nucleotide sequences differences in DNA sequence can assist in determination of divergence of evolutionary path for organisms DNA hybridization single strands of DNA anneal 16S ribonucleic acid comparing sequence of ribosomal RNA relatedness to other organisms can be determined using numerical taxonomy determined by the percentage of characteristics two organisms have in common The more you have in common phenotypically with another organism the closer related you are to that organism.
Genotypic Characteristics for Identifying Prokaryotes PCR: polymerase chain reaction used to detect small amounts of DNA present in a sample (blood, food, soil) the PCR chain reaction is used to amplify the amount of DNA present