Microbial biodegradation

About: Microbial biodegradation is a research topic. Over the lifetime, 1647 publications have been published within this topic receiving 75473 citations.

Microbial growth and substrate utilization kinetics

Abstract: Microbial growth on and utilization of environmental contaminants as substrates have been studied by many researchers. Most times, substrate utilization results in removal of chemical contaminant, increase in microbial biomass and subsequent biodegradation of the contaminant. These are all aimed at detoxification of the environmental pollutants. Several microbial growth and biodegradation kinetic models have been developed, proposed and used in bioremediation schemes. Some of these models include Monod’s, Andrews, Bungay’s weighted model, general substrate inhibition models (GSIM) and sum kinetic models. Most research on microbial potentials to degrade chemical pollutants has been performed on a laboratory scale. There is a need to extend such studies to pilot scale as well as to full-scale field applications. Key words: Microbial growth, substrate utilization, biodegradation, kinetics, detoxification, organic contaminants, models, environmental pollutants.

The Tomato Rhizosphere, an Environment Rich in Nitrogen-Fixing Burkholderia Species with Capabilities of Interest for Agriculture and Bioremediation

Abstract: It is well known that hundreds of thousands of bacterial species remain to be discovered and cultured, representing a substantial reservoir of genetic diversity and great potential for biotechnological applications. Although most of the bacteria inhabiting common environments (e.g., agricultural soils and plants) have not yet been grown in culture, many of them could be cultivated using standard methods. However, for many environments, research on microbial taxonomy and ecology is lacking. Unfortunately, novel bacterial species are often described based on the analysis of a very limited set of isolates (59), commonly one to three. This is true for many bacterial species, including several belonging to the genus Burkholderia. For example, the species B. kururiensis (80), B. sacchari (9), B. phenoliruptrix (16), B. terrae (79), B. tuberum, and B. phymatum (73) were recently described on the basis of a single isolate analyzed, and consequently, their environmental distribution and ecological role are unknown. B. kururiensis and B. sacchari were described as species with abilities to degrade trichloroethylene and to biotechnologically produce polyhydroxyalkanoic acids, respectively, but new studies related to their ecologies or applications are largely lacking. The nitrogen-fixing species B. xenovorans was described on the basis of three isolates (32); strain LB400T was isolated from polychlorinated biphenyl (PCB)-contaminated soil in Moreau, NY, strain CAC-124 was isolated from the rhizosphere of a coffee plant cultivated in Veracruz, Mexico, and strain CCUG 28445 was recovered from a blood culture in Sweden. Although strain LB400T is the best-studied PCB degrader, and its pathways for degradation of these compounds have been extensively characterized at the genetic and molecular levels (25, 35), strains CAC-124 and CCUG 28445 have been only partially analyzed and do not share the biphenyl-biodegrading capacities of strain LB400T (32). Recently, one B. xenovorans isolate was recovered from the rhizosphere of maize cultivated in The Netherlands (62). Although the complete genome of B. xenovorans LB400T was recently sequenced (12), it is noteworthy that the four extant B. xenovorans strains described in diverse studies have been randomly recovered from different environments and widely distant geographical regions, and there are no studies on the distribution of this PCB-degrading, nitrogen-fixing species or its association with plants. Emphasis has been given to studies of the isolation, taxonomy, and distribution of Burkholderia species related to human opportunistic pathogens, especially the B. cepacia complex species found in cystic fibrosis patients (33, 45, 52; for reviews, see references 15 and 42). In contrast, few studies have been performed on the overall diversity of the genus Burkholderia (61, 63), even though nonpathogenic Burkholderia species are frequently recovered from different environments (6, 40, 70), and despite their biotechnological potential in bioremediation and other applications (34, 70; for a review, see reference 48). Knowledge of novel diazotrophic Burkholderia species (11, 32, 50, 54), including legume nodule symbionts (14, 73), phylogenetically greatly distant from the B. cepacia complex species, has come very recently, but their environmental distribution and relevant features for agronomic and environmental applications are little known (13, 27, 32, 49). Bacteria are involved in degradation processes of many aromatic compounds released into the environment by the decay of plant material or by anthropogenic activity. Phenolic compounds and polymers containing benzene rings (e.g., lignins) are natural aromatic compounds (21, 29). However, phenol is a man-made aromatic compound and along with its derivatives is considered a major hazardous compound in industrial wastewater. Similarly, aromatic hydrocarbons like benzene and toluene are common pollutants of soil and groundwater (78). Soil microorganisms are capable of using aromatic compounds as sole carbon sources, owing to aerobic biodegradation catalyzed by mono- or dioxygenases (3, 78). In the last few years, rhizoremediation (microbial degradation of hazardous compounds in the rhizosphere) and phytoremediation (the use of plants to extract and degrade harmful substances) have been considered alternatives for decontamination of soils. In addition, bacteria are able to exert positive effects on plants through various mechanisms. For instance, nitrogen fixation (the natural transformation of atmospheric N2 to ammonia) contributes organic nitrogen for plant growth (28), while the bacterial enzyme 1-amino-cyclopropane-1-carboxylate (ACC) deaminase hydrolyzes ACC (the immediate precursor of ethylene) and lowers the levels of ethylene produced in developing or stressed plants, promoting root elongation (30). Some bacteria solubilize insoluble minerals through the production of acids, increasing the availability of phosphorus and other nutrients to plants in deficient soils (55). Several bacteria improve plant growth through suppression of pathogens by competing for nutrients, by antibiosis, or by synthesizing siderophores, which can solubilize and chelate iron from the soil and inhibit the growth of phytopathogenic microorganisms (23). This work was aimed at revealing the occurrence of nitrogen-fixing Burkholderia species associated with tomato (Lycopersicon esculentum) plants cultivated in different locations in Mexico. We found that the rhizosphere of tomato is a reservoir of different known and unknown diazotrophic Burkholderia species that are able to exhibit in vitro some activities involved in bioremediation, plant growth promotion, and biological control.

A review of bacterial degradation of pesticides

Abstract: Pesticide fate in the environment is affected by microbial activity. Some pesticides are readily degraded by microorganisms, others have proven to be recalcitrant. A diverse group of bacteria, including members of the genera Alcaligenes, Flavobacterium, Pseudomonas and Rhodococcus, metabolize pesticides. Microbial degradation depends not only on the presence of microbes with the appropriate degradative enzymes, but also on a wide range of environmental parameters. This review describes recent advances in biodegradation of pesticides by addressing the biology and molecular characterization of some pesticide degrading bacteria.

Influence of surfactants on microbial degradation of organic compounds

Abstract: Surfactants have the ability to increase aqueous concentrations of poorly soluble compounds and interfacial areas between immiscible fluids, thus potentially improving the accessibility of these substrates to microorganisms. However, both enhancements and inhibitions of biodegradation of organic compounds in the presence of surfactants have been reported. The mechanisms behind these phenomena are not well understood. To better understand the factors involved and the current state of knowledge in this field, a search of the literature concerning the influence of commercial surfactants and biosurfactants on microbial metabolism has been conducted. Factors pertaining to surfactant‐substrate interactions such as emulsification, solubilization, and partitioning of hydrocarbons between phases, all of which can influence accessibility of substrates to microorganisms, are of concern. Also, due to the direct interaction of surfactants with microorganisms, it appears that steric or conformational compatibi...