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Outdoor Air Sampling Techniques
Published in Christopher S. Cox, Christopher M. Wathes, Bioaerosols Handbook, 2020
Two-stage Andersen samplers loaded with plastic Petri dishes containing 27 mL trypticase soy agar + 0.5 mg cycloheximide mL-1 or Littman’s oxgall medium210 + antibiotics, were used to make weekly collections of airborne bacteria and fungi at 17 stations in suburban Washington, D.C.176 After collection, colonies were counted directly on the collection medium or transferred to other media by replica plating to aid identification. Sampling location, location characteristics (local traffic, ground cover, etc.), time of day, day of the week, rainfall and relative humidity affected catches significantly, while wind speeds >3.1 m s-1 gave larger than average particle concentrations. Again, bacteria were most numerous in summer and autumn, and fewest in winter. Bacteria at parkland and street sites in Stockholm were collected using six stage Andersen samplers, loaded with tryptone glucose agar + 50 μg cycloheximide mL-1 medium covered with 0.2% oxyethylene docosanol (OED; 0.1 mL per plate) to prevent drying and operated for 30 or 60 min 2 or 10 m above ground level.34 A diverse range of bacteria was isolated at 2 m height averaging 763 and 850 cfu m-3, respectively Half were in particles >8μm. Concentrations at 10 m were about 90% of those at 2 m. The bacteria were classified by numerical taxonomic analysis of 50 U characters. Few isolates clustered, suggesting that no group predominated but rather that there were small numbers of many types.11
Application of Genetic Engineering to the Field of Bioremediation
Published in Donald L. Wise, Debra J. Trantolo, Remediation of Hazardous Waste Contaminated Soils, 2018
Alan R. Harker, Youngjun Kim, Udayakumar Matrubutham
Exconjugants were transferred by replica plating to MMO agar plate containing phenol (0.05%), casamino acids (0.3%), Km and Rif, and to the same medium without casamino acids. Casamino acids supported the growth of the cells on phenol-containing medium, and the phenol-utilizing cells turned a dark brown color on this medium due to the formation and autooxidation of catechol. This was an effective preliminary screen for phenol nonutilizing mutants. Limited growth of the transconjugants on phenol as sole carbon source made clear isolation of mutants difficult. Thirty-six Kmr Cms colonies failed to grow on phenol as a sole carbon source. The mutants showing no growth on phenol or no catechol accumulation were replica plated to the MMO plus benzoate (0.05%) medium with Km and Rif. Several mutants that showed growth on this medium was selected for further analysis. This screening procedure was adopted because benzoate and phenol are both catabolized via catechol. The results of enzyme assays using these two metabolites demonstrated that both of the catechol 1,2-dioxygenase for ortho-ring cleavage of catechol and the catechol 2,3-dioxygenase for meta-ring cleavage pathway were induced in A. eutrophus AE0106 strain. A mutation that allows growth on benzoate but not on phenol should be deficient only in phenol hydroxylase.
A comparative study of the wild and mutated heavy metal resistant Klebsiella variicola generated for cadmium bioremediation
Published in Bioremediation Journal, 2018
Feruke-Bello Yetunde Mutiat, Babalola Gbolahan, Odeyemi Olu
The replica plating method was used and this involved the transfer of the bacteria mutant colonies from the master plate using a velveteen pad to MSA plates incorporated with different concentrations of heavy metals (to determine the MTC). The plates were incubated at 30°C for 24 – 48 h.