Category: Lab Notes: Microbiology

1885: Theodor Escherich isolates and describes Bacterium coli commune (later renamed Escherichia coli) from infant stool samples. This discovery marks…

Laboratory strains of Escherichia coli represent specialized variants that have been developed and optimized for research and biotechnology applications. These…

Plasmids occur naturally in a variety of hosts, primarily bacteria but also archaea and eukaryotes.  In bacteria, plasmids are often…

Criteria Bacteriostatic Activity Bactericidal Activity Remarks Definition Inhibits the growth and reproduction of bacteria without directly killing them Kills bacteria,…

Dysbiosis refers to an imbalance in the composition of the microbiota, the diverse community of microorganisms including bacteria, fungi, viruses,…

A small-scale plasmid isolation procedure, the miniprep, yields a sufficient amount of plasmid for the screening of clones by restriction…

Linear plasmids represent a unique category of extrachromosomal genetic elements that differ from the more common circular plasmids in both…

MRS broth is nutrients rich liquid medium for the cultivation of Lactobacilli. It was developed by de Man, Rogosa, and…

Large-scale isolation of plasmid requires a large volume of E. coli culture. Large scale plasmid isolation procedures are termed, midiprep (25 – 50 ml starting culture volume) and maxiprep (100 – 500 ml starting culture volume). A starter culture is initially prepared by inoculating a colony in a small volume (2 – 10 ml) of culture medium. Large culture volume is prepared by diluting starter culture in a ratio of 1: 100 to 1: 1000 in the growth medium.

Lambda-agar is nothing but a lambda broth which is solidified by agar. Agar is a solidifying agent. It melts at 85°C but melton agar stays liquid at a temperature > 40°C (this property is called hysteresis, different temperatures for melting and solidifying). This allows us to add heat-labile medium supplements such as antibiotics and vitamins and prepare solid medium. Lambda-agar solid medium is prepared by dissolving 15 g agar / liter of Lambda broth.

OVERVIEW TNT medium is a moderately rich medium. It contains tryptone, sodium chloride (NaCl) and thiamine. Tryptone provides basic nutrients…

OVERVIEW M9 minimal medium is a chemically-defined minimal growth medium, used to cultivate Escherichia coli. It is prepared by supplementing…

Escherichia coli, commonly referred to as E. coli, is a Gram-negative, facultative anaerobic bacterium that belongs to the Enterobacteriaceae family. …

SOC (Super Optimal broth with Catabolite repression) medium is a nutrient-rich microbial growth medium, formulated by Douglas Hanahan in 1983 (Hanahan, 1983). SOC medium is prepared without Mg++ and Glucose by dissolving 20 g bacto-tryptone, 5 g bacto-yeast extract, 2 ml of 5M sodium chloride, and 2.5 ml of 1M KCl in water to a final volume of ≈ 1000 ml (960 ml). Magnesium salts (i.e., MgSO4 and MgCl2, 10 ml each of 1M MgSO4 and 1M MgCl2) and Glucose (10 ml of 1 M Glucose) are added to the medium after autoclaving to prevent any chemical reactions and precipitation of the medium components, and degradation of Glucose.

LB is a rich growth medium, commonly used to grow E. coli. LB Luria Broth contains 1% Bacto-tryptone, 0.5% Bacto-yeast extract and 0.05% Sodium chloride. A 1000 ml LB Luria Broth is prepared by dissolving 10 g Bacto-tryptone, 5 g Bacto-yeast extract and 0.5 g sodium chloride in deionized water to a final volume of 1000 ml. After adjusting the pH 7.0 with 5N NaOH medium is autoclaved and stored in a cold room.