Which organism(s) is/are acid-fast? a. nocardia b. pseudomonas c. e. coli d. mycobacterium e. nocardia and mycobacterium

E. Nocardia AND Mycobacterium

Explanation:

Acid fast organisms are not able to take up acid based stains like gram stain. They can be bacteria or eukaryotic organisms. Mechanism for acid fastness is different for each species. The most well understood mechanism is by the tuberculosis causing bacteria Mycobacterium which has high mycolic acid content in their cell wall which leads to poor absorption of dye. Nocardia is partially acid fast.Thus for identification of acid fast organisms other stains like Ziehl-Neelsen stain are used. It stains the organism bright red in blue background.

explanation: grsaa

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.