Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons. The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized. New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems. By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented. Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times ( 2 S and sulfoxides from petrochemical waste streams. Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved. Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments.

Recent Advances in Petroleum Microbiology

Aromatic compounds are both common growth substrates for microorganisms and prominent environmental pollutants. The crucial step in their degradation is overcoming the resonance energy that stabilizes the ring structure. The classical strategy for degradation comprises an attack by oxygenases that hydroxylate and finally cleave the ring with the help of activated molecular oxygen. Here, we describe three alternative strategies used by microorganisms to degrade aromatic compounds. All three of these methods involve the use of CoA thioesters and ring cleavage by hydrolysis. However, these strategies are based on different ring activation mechanisms that consist of either formation of a non-aromatic ring-epoxide under oxic conditions, or reduction of the aromatic ring under anoxic conditions using one of two completely different systems.

/pdf/microbial-degradation-of-aromatic-compounds-from-one-1uyafyshep.pdf

Microbial degradation of aromatic compounds — from one strategy to four

Biosurfactants production and possible uses in microbial enhanced oil recovery and oil pollution remediation: a review

http://bioinformatica.uab.es/biocomputacio/treballs02-03/rburgos/dades/articulos/anarerobicdegradation.pdf

Anaerobic biodegradation of saturated and aromatic hydrocarbons.

Dissimilatory Sulfate- and Sulfur-Reducing Prokaryotes

Toluene is degraded anoxically to CO2 by the denitrifying bacterium Thauera aromatica. Toluene first becomes oxidized to benzoyl-CoA by O2-independent reactions. Benzoyl-CoA is then reduced to non-aromatic products by benzoyl-CoA reductase. We set out to study the reactions employed for the initial activation of toluene and its oxidation to the level of benzoate. Evidence is provided for a novel way of toluene degradation based on experiments with cell-free extracts and with whole toluene-grown cells: Cell-free extracts oxidized [14C]toluene to [14C]benzoyl-CoA via several radioactive intermediates. This reaction was strictly dependent on the presence of fumarate, coenzyme A and nitrate as electron acceptor; acetyl-CoA and ATP were not necessary for the reaction. The first product formed in vitro was benzylsuccinate; (2H8)toluene was converted to (2H7)benzylsuccinate. Formation of benzylsuccinate from toluene was independent of coenzyme A and nitrate, but it required the presence of fumarate. Other tricarboxylic acid cycle intermediates were converted to fumarate in cell extracts and therefore could partially substitute for fumarate. [14C]Benzylsuccinate was oxidized further to [14C]benzoyl-CoA and [14C]benzoate in cell extracts if coenzyme A and nitrate were present. No benzyl alcohol and benzaldehyde and no phenylpropionate could be detected as intermediates. In isotope trapping experiments with cell suspensions, two intermediates from [14C]toluene were detected, benzoate and benzylsuccinate. This corroborates the sequence of reactions deduced from in vitro experiments. A hypothetical degradation pathway for the anaerobic oxidation of toluene to benzoyl-CoA via an initial addition of fumarate to the methyl group of toluene and following beta-oxidation of the benzylsuccinate formed is suggested.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1996.0661w.x

Evidence that anaerobic oxidation of toluene in the denitrifying bacterium Thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate.

Reform of the U.S. welfare system in 1996 spurred claims that cuts to welfare programs effectively incentivized single mothers to find employment. It is difficult to assess the veracity of those claims, however, absent evidence of how the relationship between welfare benefits and single mother employment generalizes across countries. This study combines data from the European Union Labour Force Survey and the U.S. Current Population Survey (1992-2015) into one of the largest samples of single mothers ever, testing the relationships between welfare generosity and single mothers’ employment and work hours. We find no consistent evidence of a negative relationship between welfare generosity and single mother employment outcomes. Rather, we find tremendous cross-national heterogeneity, which does not clearly correspond to well-known institutional variations. Our findings demonstrate the limitations of single country studies and the pervasive, salient interactions between institutional contexts and social policies.

/pdf/cross-national-variation-in-the-relationship-between-welfare-1429pwez.pdf

Cross-National Variation in the Relationship between Welfare Generosity and Single Mother Employment

The authors use Current Population Survey 2016 to 2021 quarterly data to analyze changes in household joblessness across metropolitan areas in the United States during the coronavirus disease 2019 pandemic. The authors first use shift-share analysis to decompose the change in household joblessness into changes in individual joblessness, household compositions, and polarization. The focus is on polarization, which is the result of the unequal distribution of individual joblessness across households. The authors find that the rise in household joblessness during the pandemic varies strongly across U.S. metropolitan areas. The initial stark increase and subsequent recovery are due largely to changes in individual joblessness. Polarization contributes notably to household joblessness but to varying degree. Second, the authors use metropolitan area–level fixed-effects regressions to test whether the educational profile of the population is a helpful predictor of changes in household joblessness and polarization. They measure three distinct features: educational levels, educational heterogeneity, and educational homogamy. Although much of the variance remains unexplained, household joblessness increased less in areas with higher educational levels. The authors show that how polarization contributes to household joblessness is shaped by educational heterogeneity and educational homogamy.

Household Joblessness in U.S. Metropolitan Areas during the COVID-19 Pandemic: Polarization and the Role of Educational Profiles

This study investigates the extent to and mechanisms through which Matthew effects create persistent status hierarchies. We propose a model that highlights the role of cumulative status bias in the feedback loop that leads from initial status allocation to status confirmation. We investigate the formalized process of repeated status allocation in annual elections to the National Basketball Association (NBA) All-Star game. Using detailed records on player performances allows us to isolate the Matthew effect from actual productivity differences to show that a previous All-Star nomination improves the chances to be re-nominated. We demonstrate that this Matthew effect is partly explained by improved productivity after an All-Star nomination, but voters’ evaluations are also directly biased by a player’s prior status. Multiple previous nominations further improve a player’s chances, confirming the importance of cumulative status bias. The resulting status-biased persistence of achieved status implies ever greater decoupling of productivity and status, undermining the meritocratic allocation of status and resources even more than the existing literature acknowledges.

https://doi.org/10.1177/00031224231159139

Thomas Biegert

Papers

Evidence that anaerobic oxidation of toluene in the denitrifying bacterium Thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate.

Cross-National Variation in the Relationship between Welfare Generosity and Single Mother Employment

Household Joblessness in U.S. Metropolitan Areas during the COVID-19 Pandemic: Polarization and the Role of Educational Profiles

They Can’t All Be Stars: The Matthew Effect, Cumulative Status Bias, and Status Persistence in NBA All-Star Elections