Evidence for a bimodal distribution of Escherichia coli doubling times below a threshold initial cell concentration

Salmonella enterica is well-known for its ability to survive and persist in low-moisture environments. Previous studies have indicated a link between the initial cell concentration and the population of Salmonella that survive upon desiccation and subsequent storage; however, how the initial cell concentration affects survival is unknown. This study examined the basis of this phenomena and whether it occurred in other microorganisms, specifically Shiga toxigenic Escherichia coli (STEC), and Enterococcus faecium . Salmonella, STEC, and E. faecium were grown as lawns on TSAYE and harvested using buffered peptone water (BPW). To determine recovery at different initial cell levels, cultures were diluted to 9, 7, and 5 log CFU/mL and applied to filters. Filters were dried for 24 h, then stored for 28 d at 25°C/33% RH. During storage, cells were recovered from filters using BPW and cultivated on TSAYE. Both Salmonella and E. coli , but not E. faecium , showed non-proportional recovery. Less viability remained with lower initial starting population after 24 h desiccation such that ≥10 log CFU/mL were recovered when 11 log CFU/mL was desiccated, but <3 log CFU/mL were recovered when 5 log CFU/mL was desiccated. Once dried, persistence did not appear affected by initial cell concentration. When dead cells (heat-treated) were added to the diluent, recovery of Salmonella was proportional with respect to the initial cell concentration. To further examine the response on desiccation, Salmonella was diluted in BPW containing one of 11 different test cell components related to quorum sensing or known to affect desiccation resistance to assess recovery and persistence. Of the 11 additions only cell debris fractions, cell-free extract, and peptidoglycan improved recovery of Salmonella . Desiccation survival appears related to cell wall components, however, the exact mechanism affecting survival remains unknown.

Download Full-text

The comparison of trichloroethylene removal rates by methane- and aromatic-utilizing microorganisms

Water Science & Technology ◽

10.2166/wst.1998.0272 ◽

1998 ◽

Vol 38 (7) ◽

pp. 19-24 ◽

Cited By ~ 3

Author(s):

C.-J. Lu ◽

C. M. Lee ◽

M.-S. Chung

Keyword(s):

Cell Concentration ◽

Removal Rate ◽

Carbon Sources ◽

Batch Reactors ◽

Initial Cell Concentration ◽

Removal Rates ◽

Initial Cell ◽

Toluene Concentration ◽

Cell Source ◽

Removal Efficiencies

The comparison of TCE cometabolic removal by methane, toluene, and phenol utilizers was conducted with a series of batch reactors. Methane, toluene, or phenol enriched microorganisms were used as cell source. The initial cell concentration was about 107 cfu/mL. Methane, toluene, and phenol could be readily biodegraded resulting in the cometabolic removal of TCE. Among the three primary carbon sources studied, the presence of phenol provided the best cometabolic removal of TCE. When the concentration of carbon source was 3 mg-C/L, the initial TCE removal rates initiated by methane, toluene, and phenol utilizers were 1.5, 30, and 100 μg/L-hr, respectively. During the incubation period of 80 hours, TCE removal efficiencies were 26% and 96% with the presence of methane and toluene, respectively. However, it was 100% within 20 hours with the presence of phenol. For phenol utilizers, the initial TCE removal rates were about the same, when the phenol concentrations were 1.35, 2.7, and 4.5 mg/L. However, TCE removal was not proportional to the concentrations of phenol. TCE removal was hindered when the phenol concentration was higher than 4.5 mg/L because of the rapid depletion of dissolved oxygen. The presence of toluene also initiated cometabolic removal of TCE. The presence of toluene at 3 and 5 mg/L resulted in similar TCE removal. The initial TCE removal rate was about 95 μg/L-hr at toluene concentrations of 3 and 5 mg/L compared to 20 μg/L-hr at toluene concentration of 1 mg/L.

Download Full-text

Effect of protective agents, rehydration media and initial cell concentration on viability of Pantoea agglomerans strain CPA-2 subjected to freeze-drying

Journal of Applied Microbiology ◽

10.1046/j.1365-2672.2000.01182.x ◽

2000 ◽

Vol 89 (5) ◽

pp. 793-800 ◽

Cited By ~ 118

Author(s):

E. Costa ◽

J. Usall ◽

N. Teixido ◽

N. Garcia ◽

I. Vinas

Keyword(s):

Freeze Drying ◽

Cell Concentration ◽

Pantoea Agglomerans ◽

Initial Cell Concentration ◽

Initial Cell ◽

Protective Agents

Download Full-text

Studies of the recovery of frozen Salmonella gallinarum: the roles of cooling rate, initial cell concentration and plating medium*

International Journal of Food Science & Technology ◽

10.1111/j.1365-2621.1973.tb01708.x ◽

2007 ◽

Vol 8 (2) ◽

pp. 211-216 ◽

Cited By ~ 7

Author(s):

M. RACCACH ◽

B. JUVEN

Keyword(s):

Cooling Rate ◽

Cell Concentration ◽

Initial Cell Concentration ◽

Salmonella Gallinarum ◽

Initial Cell

Download Full-text

THE EFFECT OF THE INITIAL CELL CONCENTRATION UPON SURVIVAL OF BACTERIA AT −22 C

Journal of Bacteriology ◽

10.1128/jb.69.3.244-249.1955 ◽

1955 ◽

Vol 69 (3) ◽

pp. 244-249 ◽

Cited By ~ 19

Author(s):

Cecil P. Major ◽

John D. McDougal ◽

Arthur P. Harrison

Keyword(s):

Cell Concentration ◽

Initial Cell Concentration ◽

Initial Cell

Download Full-text

The Effect of Initial Cell Concentration on Xylose Fermentation by Pichia stipitis

Applied Biochemistry and Biotecnology ◽

10.1007/978-1-60327-181-3_53 ◽

2007 ◽

pp. 653-662 ◽

Cited By ~ 1

Author(s):

Frank K. Agbogbo ◽

Guillermo Coward-Kelly ◽

Mads Torry-Smith ◽

Kevin Wenger ◽

Thomas W. Jeffries

Keyword(s):

Xylose Fermentation ◽

Cell Concentration ◽

Pichia Stipitis ◽

Initial Cell Concentration ◽

Initial Cell

Download Full-text

The Growth ofMonoraphidiumsp. andScenedesmussp. Cells in the Presence of Thorium

The Scientific World JOURNAL ◽

10.1100/2012/592721 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Juliana Cristina de Queiroz ◽

Ana Cristina de Melo Ferreira ◽

Antonio Carlos Augusto da Costa

Keyword(s):

Cell Concentration ◽

Direct Count ◽

Initial Cell Concentration ◽

Initial Cell ◽

Count Method ◽

Low Concentrations ◽

Direct Counting ◽

Presence And Absence ◽

Positive Effect

Toxicity of thorium byMonoraphidiumsp. andScenedesmussp. was studied. Microalgal cultures were inoculated in ASM-1 medium in presence and absence of thorium. Its effect was monitored by direct counting on Fuchs-Rosenthal chamber and with software. The toxicity of thorium over the species was observed for concentrations over 50.0 mg/L. After 30 days,Monoraphidiumcells decreased their concentration from4.23×106to4.27×105and8.57×105 cells/mL, in the presence of 50.0 and 100.0 mg/L of thorium, respectively.Scenedesmussp. cells were more resistant to thorium: for an initial cell concentration of7.65×104 cells/mL it was observed a change to5.25×105and5.12×105 cells/mL, in the presence of thorium at 50.0 and 100.0 mg/L, respectively. This is an indication that low concentrations of the radionuclide favored the growth, and thatScenedesmuscells are more resistant to thorium thanMonoraphidiumcells. The software used for comparison with direct count method proved to be useful for the improvement of accuracy of the results obtained, a decrease in the uncertainty and allowed recording of the data. The presence of thorium suggests that low concentrations have a positive effect on the growth, due to the presence of the nitrate, indicating its potential for ecotoxicological studies.

Download Full-text