Isolation of Alcaligenes sp. strain L6 at low oxygen concentrations and degradation of 3-chlorobenzoate via a pathway not involving (chloro)catechols

Abstract

Isolations of 3-chlorobenzoate (3CBA)-degrading aerobic bacteria under reduced O 2 partial pressures yielded organisms which metabolized 3CBA via the gentisate or the protocatechuate pathway rather than via the catechol route. The 3CBA metabolism of one of these isolates, L6, which was identified as an Alcaligenes species, was studied in more detail. Resting-cell suspensions of L6 pregrown on 3CBA oxidized all known aromatic intermediates of both the gentisate and the protocatechuate pathways. Neither growth on nor respiration of catechol could be detected. Chloride production from 3CBA by L6 was strictly oxygen dependent. Cell-free extracts of 3CBA-grown L6 cells exhibited no catechol dioxygenase activity but possessed protocatechuate 3,4-dioxygenase, gentisate dioxygenase, and maleylpyruvate isomerase activities instead. In continuous culture with 3CBA as the sole growth substrate, strain L6 demonstrated an increased oxygen affinity with decreasing steady-state oxygen concentrations.

Characterization of 3-chlorobenzoate degrading aerobic bacteria isolated under various environmental conditions

“…Enrichments in continuous culture resulted in dominance of gp-type bacteria at low dilution rates (0.025 h 31 ). At high oxygen concentrations plus 3-chlorobenzoate limitation, these bacteria appeared to have a competitive advantage over the cat-type bacteria, probably due to lower 3CBA a¤nities of the latter, as shown previously [13,16]. In addition, the higher a¤nities for oxygen that are characteristic of these newly isolated gp-type bacteria probably resulted in their dominance under oxygen limiting conditions.…”

“…Microtiter plates which were used for MPN counts, and agar plates (LMM+BA or 3CBA) were incubated in a jar with a gas phase that contained either 98% nitrogen plus 2% oxygen (MPN counts) or air (approximately 20% O 2 ). Growth in continuous culture, under oxygen limited conditions or substrate limiting conditions, were performed in oxygen regulated chemostats as described previously [16].…”

“…Isolates obtained from chemostat enrichments were cultivated in batch culture prior to the determination of the respiration rates with catechol, gentisate, or protocatechuate as substrates. In addition, the activities of key enzymes of these pathways, ortho-and meta-(chloro)catechol dioxygenase [20], 2,3-, 4,5-and 3,4-protocatechuate dioxygenase [21] and gentisate dioxygenase [22] were determined in cell free extracts from cells grown in batch culture with (chloro)catechol, protocatechuate and gentisate as substrates, respectively [16].…”

Reversible accumulation of p-hydroxybenzoate and catechol determines the sequential decomposition of phenolic compounds in mixed substrate cultivations in pseudomonads

“…Activities of C12O and C23O were measured spectrophotometrically by monitoring formation of reaction products at 260 and 375 nm, respectively [26,27]. PC34O activity was measured by determining the decrease of absorption at 290 nm due to the oxidation of protocatechuate [28]. Protein was measured by the method of Bradford [29] with bovine serum albumin as a standard.…”

2‐Chlorobenzoate Biodegradation by Recombinant Burkholderia cepacia under Hypoxic Conditions in a Membrane Bioreactor

“…However, high biomass concentration and, consequently, higher liquid temperatures due to metabolic heat in aerobic MBR systems reduce oxygen solubility in water as well as the availability of oxygen to the cells in the flocs. Oxygen is required not only as a terminal electron acceptor in respiration, but also as a substrate for oxygenases in the metabolism of many toxic aromatic compounds (Krooneman et al, 1996). Low dissolved oxygen or hypoxic conditions in the bioreactor also could lead to metabolic intermediates that inhibit complete mineralization of aromatic contaminants such as halogenated organics.…”