Biomedical subjects

Miriam L Land

Publications and source records attributed to Miriam L Land.

5 recordsLinked to original sources

PubMed2006

Genome sequence of the chemolithoautotrophic nitrite-oxidizing bacterium Nitrobacter winogradskyi Nb-255.

The alphaproteobacterium Nitrobacter winogradskyi (ATCC 25391) is a gram-negative facultative chemolithoautotroph capable of extracting energy from the oxidation of nitrite to nitrate. Sequencing and analysis of its genome revealed a single circular chromosome of 3,402,093 bp encoding 3,143 predicted proteins. There were extensive similarities to genes in two alphaproteobacteria, Bradyrhizobium japonicum USDA110 (1,300 genes) and Rhodopseudomonas palustris CGA009 CG (815 genes). Genes encoding pathways for known modes of chemolithotrophic and chemoorganotrophic growth were identified. Genes encoding multiple enzymes involved in anapleurotic reactions centered on C2 to C4 metabolism, including a glyoxylate bypass, were annotated. The inability of N. winogradskyi to grow on C6 molecules is consistent with the genome sequence, which lacks genes for complete Embden-Meyerhof and Entner-Doudoroff pathways, and active uptake of sugars. Two gene copies of the nitrite oxidoreductase, type I ribulose-1,5-bisphosphate carboxylase/oxygenase, cytochrome c oxidase, and gene homologs encoding an aerobic-type carbon monoxide dehydrogenase were present. Similarity of nitrite oxidoreductases to respiratory nitrate reductases was confirmed. Approximately 10% of the N. winogradskyi genome codes for genes involved in transport and secretion, including the presence of transporters for various organic-nitrogen molecules. The N. winogradskyi genome provides new insight into the phylogenetic identity and physiological capabilities of nitrite-oxidizing bacteria. The genome will serve as a model to study the cellular and molecular processes that control nitrite oxidation and its interaction with other nitrogen-cycling processes.

Bacterial Proteins↗

PubMed2005

Global profiling of Shewanella oneidensis MR-1: expression of hypothetical genes and improved functional annotations.

The gamma-proteobacterium Shewanella oneidensis strain MR-1 is a metabolically versatile organism that can reduce a wide range of organic compounds, metal ions, and radionuclides. Similar to most other sequenced organisms, approximately 40% of the predicted ORFs in the S. oneidensis genome were annotated as uncharacterized "hypothetical" genes. We implemented an integrative approach by using experimental and computational analyses to provide more detailed insight into gene function. Global expression profiles were determined for cells after UV irradiation and under aerobic and suboxic growth conditions. Transcriptomic and proteomic analyses confidently identified 538 hypothetical genes as expressed in S. oneidensis cells both as mRNAs and proteins (33% of all predicted hypothetical proteins). Publicly available analysis tools and databases and the expression data were applied to improve the annotation of these genes. The annotation results were scored by using a seven-category schema that ranked both confidence and precision of the functional assignment. We were able to identify homologs for nearly all of these hypothetical proteins (97%), but could confidently assign exact biochemical functions for only 16 proteins (category 1; 3%). Altogether, computational and experimental evidence provided functional assignments or insights for 240 more genes (categories 2-5; 45%). These functional annotations advance our understanding of genes involved in vital cellular processes, including energy conversion, ion transport, secondary metabolism, and signal transduction. We propose that this integrative approach offers a valuable means to undertake the enormous challenge of characterizing the rapidly growing number of hypothetical proteins with each newly sequenced genome.

Gene Expression Profiling↗

PubMed2005

Whole-genome analyses of speciation events in pathogenic Brucellae.

Despite their high DNA identity and a proposal to group classical Brucella species as biovars of Brucella melitensis, the commonly recognized Brucella species can be distinguished by distinct biochemical and fatty acid characters, as well as by a marked host range (e.g., Brucella suis for swine, B. melitensis for sheep and goats, and Brucella abortus for cattle). Here we present the genome of B. abortus 2308, the virulent prototype biovar 1 strain, and its comparison to the two other human pathogenic Brucella species and to B. abortus field isolate 9-941. The global distribution of pseudogenes, deletions, and insertions supports previous indications that B. abortus and B. melitensis share a common ancestor that diverged from B. suis. With the exception of a dozen genes, the genetic complements of both B. abortus strains are identical, whereas the three species differ in gene content and pseudogenes. The pattern of species-specific gene inactivations affecting transcriptional regulators and outer membrane proteins suggests that these inactivations may play an important role in the establishment of host specificity and may have been a primary driver of speciation in the genus Brucella. Despite being nonmotile, the brucellae contain flagellum gene clusters and display species-specific flagellar gene inactivations, which lead to the putative generation of different versions of flagellum-derived structures and may contribute to differences in host specificity and virulence. Metabolic changes such as the lack of complete metabolic pathways for the synthesis of numerous compounds (e.g., glycogen, biotin, NAD, and choline) are consistent with adaptation of brucellae to an intracellular life-style.

Bacterial Proteins↗

PubMed2004

Construction and validation of the Rhodobacter sphaeroides 2.4.1 DNA microarray: transcriptome flexibility at diverse growth modes.

A high-density oligonucleotide DNA microarray, a genechip, representing the 4.6-Mb genome of the facultative phototrophic proteobacterium, Rhodobacter sphaeroides 2.4.1, was custom-designed and manufactured by Affymetrix, Santa Clara, Calif. The genechip contains probe sets for 4,292 open reading frames (ORFs), 47 rRNA and tRNA genes, and 394 intergenic regions. The probe set sequences were derived from the genome annotation generated by Oak Ridge National Laboratory after extensive revision, which was based primarily upon codon usage characteristic of this GC-rich bacterium. As a result of the revision, numerous missing ORFs were uncovered, nonexistent ORFs were deleted, and misidentified start codons were corrected. To evaluate R. sphaeroides transcriptome flexibility, expression profiles for three diverse growth modes--aerobic respiration, anaerobic respiration in the dark, and anaerobic photosynthesis--were generated. Expression levels of one-fifth to one-third of the R. sphaeroides ORFs were significantly different in cells under any two growth modes. Pathways involved in energy generation and redox balance maintenance under three growth modes were reconstructed. Expression patterns of genes involved in these pathways mirrored known functional changes, suggesting that massive changes in gene expression are the major means used by R. sphaeroides in adaptation to diverse conditions. Differential expression was observed for genes encoding putative new participants in these pathways (additional photosystem genes, duplicate NADH dehydrogenase, ATP synthases), whose functionality has yet to be investigated. The DNA microarray data correlated well with data derived from quantitative reverse transcription-PCR, as well as with data from the literature, thus validating the R. sphaeroides genechip as a powerful and reliable tool for studying unprecedented metabolic versatility of this bacterium.

Adaptation, Physiological↗

PubMed2003

Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris.

Rhodopseudomonas palustris is among the most metabolically versatile bacteria known. It uses light, inorganic compounds, or organic compounds, for energy. It acquires carbon from many types of green plant-derived compounds or by carbon dioxide fixation, and it fixes nitrogen. Here we describe the genome sequence of R. palustris, which consists of a 5,459,213-base-pair (bp) circular chromosome with 4,836 predicted genes and a plasmid of 8,427 bp. The sequence reveals genes that confer a remarkably large number of options within a given type of metabolism, including three nitrogenases, five benzene ring cleavage pathways and four light harvesting 2 systems. R. palustris encodes 63 signal transduction histidine kinases and 79 response regulator receiver domains. Almost 15% of the genome is devoted to transport. This genome sequence is a starting point to use R. palustris as a model to explore how organisms integrate metabolic modules in response to environmental perturbations.

Biological Transport↗