Influence of Exogenous Oxidative Stress on Escherichia Coli Cell Growth, Viability and Morphology

Abstract

The present study attempted to determine the influence of exogenous oxidative stress on the cell viability of Escherichia coli. In this regard, 3mM hydrogen peroxide (H 2 O 2) was added to the late log phase of E. coli culture, and afterwards the phenotype, cell morphology and the ability to form colony forming units (CFU) on agar plates were examined. As expected, a quick phenotypic suppression as well as a rapid decline in viable and culturable cell numbers was observed at the mid-stationary phase as compared to control. Interestingly, a large mass of cell aggregates was noticed upon addition of H 2 O 2. Thus the current investigation corroborated the previous findings and further added to the existing knowledge on oxidative stress events in E. coli.

Possible Growth Retrieval Simulation on the Heat-Stressed Pseudomonas aeruginosa (SUBP01) Cells

“…As stated earlier, after 48 hours of incubation, P. aeruginosa cells were surprisingly found to retrieve their cell turbidity at 600 nm along with the generation of the culturable cells at 45° and 46°C upon supplementation with the extracellular fractions of P. fluorescens and inorganic supplement compared to the control and those grown with the extracellular fractions of Bacillus species led us to further cross-check of the growth retrieval trait of the cells through the spot tests as stated earlier [25][26][27] . Consistent species as organic supplement which was further compared to that of (3) the inorganic supplement (Mg 2+ with EDTA) into the culture media of heat stressed P. aeruginosa (Figure 2 Earlier studies revealed that E. coli cells exhibited s E dependent cell lysis at early stationary phase, which might be one type of programmed cell death (PCD) 15,17,32 .…”

“…After adjusting optical density of the pre-culture at 600 nm (OD 600 ) to 0.1, 30 µl each was introduced into 3 different sets of minimal agar broth (30 ml) and incubated at 45° and 46°C. At every 12 hours interval, the cell growth was monitored by measuring OD 600 and by counting the colony forming units (cfu) up to 72 hours 7,[25][26][27] . Revelation of culturable cells was further confirmed by the supportive spot tests 7,25-27 .…”

“…Simple staining (crystal violet, Hucker's solution) was conducted to assess the viability and the cellular morphology as described previously [25][26][27] . An aliquot of 10 µl from the bacterial culture suspension was removed at 24 hours of growth, and the cellular morphology, shape and organization were observed under the light microscope (Optima Biological Microscope G206, Taiwan) at 1,000x magnification [25][26][27] .…”

“…An aliquot of 10 µl from the bacterial culture suspension was removed at 24 hours of growth, and the cellular morphology, shape and organization were observed under the light microscope (Optima Biological Microscope G206, Taiwan) at 1,000x magnification [25][26][27] .…”

“…In our earlier studies, the cellular impact in response to the external and internal oxidative stresses [16][17][25][26][27] and heat shock (unpublished) in E. coli, Pseudomonas spp., Bacillus spp. and Salmonella spp.…”