Microbio Final Lab Exam

PARE

Prevalence of Antibiotic-Resistance in the Environment

Actinobacteria

slow growing, filamentous bacteria widespread in soil around the world in all biomes that somewhat resembles fungi → however they are gm + prokaryotes and are anaerobic/aerobic sometimes

What is an example of actinobacteria?

Streptomyces

What does actinobacteria produce?

A wide variety of bioactive metabolites used as medicines like anitbacterials, antifungals, antivirals, tetracyclines, etc.

Streptomyces

The largest genus of the phylum actinobacteria, they have complex secondary metabolism and produce over two-thirds of the clinically useful antibiotics of natural origin.

What did we do in the first part of the soil project?

Serial dilutions onto nutrient TS agar with no antibiotic and plated 10^-1 to 10^-3 on 3 micrograms per ml tetracycline and 30 micrograms per ml tetracycline agar to see if there are any tet resistant bacteria in the soil.

How do you calculate CFU for the soil?

number of colonies x 1/dilution factor x 1/.2 because we plated 200 microliters

How do you calculate percent Tet resistant colonies as a function of CFU’s per gram soil?

The number of tet resistant colonies divided by number of colonies grown on NA.

Crowded plate technique

Simple screening technique for detecting and isolating antibiotic producing bacteria. It consists of preparing a series of dilutions of soil samples and examining growth of yeasts, and whether any antibiotic producing microorganisms can be detected.

What do you do to get a crowded plate technique?

Using molten agar deeps, add 1 mL of diluted soil to each tube (10^-1 to 10^-4) and mix the tube quickly in your hands and pouring the hot media with soil into the empty petri dishes.