What were the results of your 16S analysis?
Four of my isolates had their 16S ribosomal DNA sequenced. Based on sequence identity, two (LB 2/ PDA 5) were determined to belong to the Pseudomonas genus and one (R2A 18) to the Bacillus genus. The fourth (PDA 2) had high percent identity match to a lot of different genera, so it’s family was determined to be Enterobacteriaceae.
Does your Gram stain agree?
For reference, here is a table with my four isolates with their Gram stains and microscopic characterization:
Each of the Gram stains agree with what is typical for the determined genus/family; positive for Bacillus, and Gram negative for Pseudomonas and Enterobacteriaceae.
Pick one of your isolates and find out more about the genus (it is unlikely you will be able to determine the species).
I choose to research the Pseudomonas genus since two of my isolates belong to the genus, and they were the only isolates with working cell-free extracts.
a) General cellular and morphological characteristics of the genus (taxonomic classification, nutrition, cell shape, habitat).
Over 140 bacteria belong to the Pseudomonas genus, and are Gram negative and rod shaped. Pseudomonas are typically found in wet environments such as soil and water, but they are also commonly found in hospitals as well in locations such as respiratory equipment, sinks, and food. Additionally, they can be grown in a lab setting on most standard media types. (1)
Here is a Gram stain of a common Pseudomonas, Pseudomonas aeruginosa.(2)
b) Information regarding antibiotic production in this genus.
As for antibiotic production, papers have been published indicating specific species produce antibiotics. One in particular that I found interesting is about Pseudomonas fluorescens. This species has been isolated from cultivating soils which naturally suppress typical soil-based plant pathogens. In the study, they found and isolated four different antibiotics from Pseudomonas fluorescens: pyoluteorin, pyrrolnitrin, phenazine-1- carboxylic acid, and 2,4-diacetylphloroglucinol. (3)
Additionally, within the species Pseudomonas aeruginosa, 90 percent of strains produce a lethal toxin, called Toxin A. This toxin inhibits protein synthesis in other cells, effectively killing them. The lethal dose in mice is about 0.2 µg. (2)
I did a little more searching due to the very distinct orange pigment that my isolate produced to see if that could give any insight as to the species. However, I found that the pigments produced by pseudomonas are typically green/blue as in the case for Pseudomonas aeruginosa and Pseudomonas fluorescens. Which is interesting because one of my extracts was a green color. However, I could not find any Pseudomonas that produce a bright orange pigment.
References:
- Iglewski BH. Pseudomonas. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 27.
- http://faculty.ccbcmd.edu/courses/bio141/labmanua/lab12/Psaeruginosa.html
- Raaijmakers, J. M., Weller, D. M., & Thomashow, L. S. (1997). Frequency of antibiotic-producing Pseudomonas spp. in natural environments. Applied and Environmental Microbiology, 63(3), 881–887
