title: Effect of carbon starvation on p-nitrophenol degradation by a Moraxella strain in buffer and river water.
abstract: This study examines the effect of carbon starvation on the ability of a Moraxella sp. strain to degrade p-nitrophenol (PNP). Carbon starvation for 24 h decreased the induction time for p-nitrophenol degradation by the bacterium in a minimal salt medium from 6 to 1 h but it did not completely eliminate the induction time. Moraxella cells with 2-day carbon starvation had an induction time of 3 h and the induction time of the 3-day starved cells was 6 h. A 100% increase in density of the non-starved cells did not affect the induction time for p-nitrophenol degradation by the bacterium, indicating that the initial increase in cell density of the carbon-starved culture did not cause the faster onset of p-nitrophenol degradation. However, the initial uptake of p-nitrophenol of the 1-day carbon-starved Moraxella cells was 3-fold higher than the non-starved cells. A green fluorescent protein gene (gfp)-labelled Moraxella (M6 strain) was constructed to examine the survival of and p-nitrophenol degradation by the bacterium in non-sterile river water samples. Similar p-nitrophenol degradation behaviour was observed in the river water samples inoculated with the M6 cells. The time needed for complete degradation of p-nitrophenol by the non-starved M6 was 19-27 and 33 h in samples spiked with 80, 200 and 360 microM p-nitrophenol, respectively. However, the 1-day carbon-starved inocula required about 16 h to degrade the p-nitrophenol completely regardless of its concentration in the water samples. Survival of the carbon-starved and non-starved M6 was not significantly different from each other in the river water regardless of the p-nitrophenol concentration. In the absence of p-nitrophenol, the inoculum density decreased continuously. At 200 and 360 microM p-nitrophenol, the cell densities of M6 increased in the first two days of incubation and declined steadily afterward.
authors.affiliation: Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, Ont., Canada P7B 5E1. kam.leung@lakeheadu.ca
authors.forename: Kam Tin
authors.initials: KT
authors.lastname: Leung
authors.forename: Michael
authors.initials: M
authors.lastname: Moore
authors.forename: Hung
authors.initials: H
authors.lastname: Lee
authors.forename: Jack T
authors.initials: JT
authors.lastname: Trevors
mesh_terms: D002021:Buffers; D002244:Carbon / Q000378:metabolism* / Q000494:pharmacology; D005618:Fresh Water / Q000382:microbiology*; D009016:Moraxella / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009596:Nitrophenols / Q000378:metabolism*; D013997:Time Factors
chemical_list: D002021:Buffers; D009596:Nitrophenols; D002244:Carbon; C024836:4-nitrophenol