The DedA protein family is a highly conserved and ancient family of membrane proteins with representatives in most sequenced genomes, including those of bacteria, archaea, and eukarya. The functions of the DedA family proteins remain obscure. However, recent genetic approaches have revealed important roles for certain bacterial DedA family members in membrane homeostasis. Bacterial DedA family mutants display such intriguing phenotypes as cell division defects, temperature sensitivity, altered membrane lipid composition, elevated envelope-related stress responses, and loss of proton motive force. The DedA family is also essential in at least two species of bacteria: Borrelia burgdorferi and Escherichia coli. Here, we describe the phylogenetic distribution of the family and summarize recent progress toward understanding the functions of the DedA membrane protein family.
The DedA family is a highly conserved, ancient family of membrane proteins with representatives in most sequenced genomes. A characteristic of prokaryotic DedA family genes is extensive gene duplication, with most bacterial genomes carrying two or more homologues. The Escherichia coli genome carries eight DedA genes, each individually nonessential. We previously described an E. coli mutant (BC202; DyghB : : kan R , DyqjA : : tet R ) with in-frame deletions of two DedA genes encoding proteins with 61 % amino acid identity. BC202 fails to complete cell division or grow at elevated temperatures. Here, we report that restoration of normal growth and cell division of BC202 is possible by overexpression of a subset of the eight E. coli DedA genes (yabI, yohD, yqjA and yghB) but not others (dedA, ydjX, ydjZ and yqaA), suggesting the existence of two functional groups within the family. We have constructed individual E. coli strains in which all eight DedA genes are deleted in a nonpolar manner, and growth is supported by a single DedA family gene under control of an inducible promoter. Strain BAL801 (with growth supported by cloned dedA) and BAL802 (with growth supported by cloned yqjA) exhibit slow growth that is absolutely dependent upon the presence of the arabinose inducer. Growth in the presence of glucose results in cell death. These results indicate that while not individually essential, the E. coli DedA family proteins are collectively essential. These observations suggest important functions for the E. coli DedA protein family.
Volatilization of semi/volatile persistent organic pollutants (POPs) from soils is a major source of global POPs emission. This proof-of-concept study investigated a novel biochar-plant tandem approach to effectively immobilize and then degrade POPs in soils using hexachlorobenzene (HCB) as a model POP and ryegrass (Lolium perenne L.) as a model plant growing in soils amended with wheat straw biochar. HCB dissipation was significantly enhanced in the rhizosphere and near rhizosphere soils, with the greatest dissipation in the 2 mm near rhizosphere. This enhanced HCB dissipation likely resulted from (i) increased bioavailability of immobilized HCB and (ii) enhanced microbial activities, both of which were induced by ryegrass root exudates. As a major component of ryegrass root exudates, oxalic acid suppressed HCB sorption to biochar and stimulated HCB desorption from biochar and biochar-amended soils, thus increasing the bioavailability of HCB. High-throughput sequencing results revealed that the 2 mm near rhizosphere soil showed the lowest bacterial diversity due to the increased abundance of some genera (e.g., Azohydromonas, Pseudomonas, Fluviicola, and Sporocytophaga). These bacteria were likely responsible for the enhanced degradation of HCB as their abundance was exponentially correlated with HCB dissipation. The results from this study suggest that the biochar-plant tandem approach could be an effective strategy for remediating soils contaminated with semi/volatile organic contaminants.
Conventional microbiological methods have been readily taken over by newer molecular techniques due to the ease of use, reproducibility, sensitivity and speed of working with nucleic acids. These tools allow high throughput analysis of complex and diverse microbial communities, such as those in soil, freshwater, saltwater, or the microbiota living in collaboration with a host organism (plant, mouse, human, etc). For instance, these methods have been robustly used for characterizing the plant (rhizosphere), animal and human microbiome specifically the complex intestinal microbiota. The human body has been referred to as the Superorganism since microbial genes are more numerous than the number of human genes and are essential to the health of the host. In this review we provide an overview of the Next Generation tools currently available to study microbial ecology, along with their limitations and advantages.
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