- Home
- A-Z Publications
- Annual Review of Microbiology
- Previous Issues
- Volume 56, 2002
Annual Review of Microbiology - Volume 56, 2002
Volume 56, 2002
- Review Articles
-
-
-
Genome Remodeling in Ciliated Protozoa
Vol. 56 (2002), pp. 489–520More Less▪ AbstractThe germline genomes of ciliated protozoa are dynamic structures, undergoing massive DNA rearrangement during the formation of a functional macronucleus. Macronuclear development involves chromosome fragmentation coupled with de novo telomere synthesis, numerous DNA splicing events that remove internal segments of DNA, and, in some ciliates, the reordering of scrambled gene segments. Despite the fact that all ciliates share similar forms of DNA rearrangement, there appears to be great diversity in both the nature of the rearranged DNA and the molecular mechanisms involved. Epigenetic effects on rearrangement have also been observed, and recent work suggests that chromatin differentiation plays a role in specifying DNA segments either for rearrangement or for elimination.
-
-
-
-
Common Principles in Viral Entry
Vol. 56 (2002), pp. 521–538More Less▪ AbstractViruses occur throughout the biosphere. Cells of Eukarya, Bacteria, and Archaea are infected by a variety of viruses that considerably outnumber the host cells. Although viruses have adapted to different host systems during evolution and many different viral strategies have developed, certain similarities can be found. Viruses encounter common problems during their entry process into the host cells, and similar strategies seem to ensure, for example, that the movement toward the site of replication and the translocation through the host membrane occur. The penetration of the host cell's external envelope involves, across the viral world, either fusion between two membranes, channel formation through the host envelope, disruption of the membrane vesicle, or a combination of these events. Endocytic-type events may occur during the entry of a bacterial virus as well as during the entry of an animal virus; the same applies for membrane fusion.
-
-
-
Cross-Species Infections and Their Analysis
Vol. 56 (2002), pp. 539–565More Less▪ AbstractThe ability of certain pathogens to infect multiple hosts has led to the development of genetically tractable nonvertebrate hosts to elucidate the molecular mechanisms of interactions between these pathogens and their hosts. The use of plant, insect, nematode, and protozoan hosts to study human pathogens has facilitated the elucidation of molecular nature of pathogenesis and host responses. Analyses of virulence of multihost pathogens on their respective hosts revealed that pathogens utilize many universal offensive strategies to overcome host defenses, irrespective of the evolutionary lineage of the host. Likewise, genetic dissections of the defense response of the nonvertebrate hosts have also shown that key features underlying host defense responses are highly conserved. This review summarizes how the information gained from the analysis of cross-species infections contributes to our understanding of host-pathogen interactions.
-
-
-
Bacterial Chromosome Segregation
Vol. 56 (2002), pp. 567–597More Less▪ AbstractRecent studies have made great strides toward our understanding of the mechanisms of microbial chromosome segregation and partitioning. This review first describes the mechanisms that function to segregate newly replicated chromosomes, generating daughter molecules that are viable substrates for partitioning. Then experiments that address the mechanisms of bulk chromosome movement are summarized. Recent evidence indicates that a stationary DNA replication factory may be responsible for supplying the force necessary to move newly duplicated DNA toward the cell poles. Some factors contributing to the directionality of chromosome movement probably include centromere-like-binding proteins, DNA condensation proteins, and DNA translocation proteins.
-
-
-
Impact of Genomic Technologies on Studies of Bacterial Gene Expression
Vol. 56 (2002), pp. 599–624More Less▪ AbstractThe ability to simultaneously monitor expression of all genes in any bacterium whose genome has been sequenced has only recently become available. This requires not only careful experimentation but also that voluminous data be organized and interpreted. Here we review the emerging technologies that are impacting the study of bacterial global regulatory mechanisms with a view toward discussing both perceived best practices and the current state of the art. To do this, we concentrate upon examples using Escherichia coli and Bacillus subtilis because prior work in these organisms provides a sound basis for comparison.
-
-
-
Control of Chromosome Replication in Caulobacter Crescentus
Vol. 56 (2002), pp. 625–656More Less▪ AbstractCaulobacter crescentus permits detailed analysis of chromosome replication control during a developmental cell cycle. Its chromosome replication origin (Cori) may be prototypical of the large and diverse class of alpha-proteobacteria. Cori has features that both affiliate and distinguish it from the Escherichia coli chromosome replication origin. For example, requirements for DnaA protein and RNA transcription affiliate both origins. However, Cori is distinguished by several features, and especially by five binding sites for the CtrA response regulator protein. To selectively repress and limit chromosome replication, CtrA receives both protein degradation and protein phosphorylation signals. The signal mediators, proteases, response regulators, and kinases, as well as Cori DNA and the replisome, all show distinct patterns of temporal and spatial organization during cell cycle progression. Future studies should integrate our knowledge of biochemical activities at Cori with our emerging understanding of cytological dynamics in C. crescentus and other bacteria.
-
-
-
The Prevalence and Mechanisms of Vancomycin Resistance in Staphylococcus Aureus
Vol. 56 (2002), pp. 657–675More Less▪ AbstractThe emergence of Staphylococcus aureus resistant to vancomycin has caused considerable concern. Such strains are currently rare, although they have been isolated from many areas of the world. Considerable controversy surrounds strains of S. aureus displaying heterogeneous resistance to vancomycin regarding their definition and methods for detection. This has led to considerable variance in estimates of prevalence (0–1.3%–20% in Japan) and has hindered efforts to define the clinical relevance of these strains. The mechanism of resistance involves a complex reorganization of cell wall metabolism, leading to a grossly thickened cell wall with reduced peptidoglycan cross-linking. There may be many different ways in which strains achieve this endpoint. Current knowledge and theories are summarized.
-
-
-
Poliovirus Cell Entry: Common Structural Themes in Viral Cell Entry Pathways
Vol. 56 (2002), pp. 677–702More Less▪ AbstractStructural studies of polio- and closely related viruses have provided a series of snapshots along their cell entry pathways. Based on the structures and related kinetic, biochemical, and genetic studies, we have proposed a model for the cell entry pathway for polio- and closely related viruses. In this model a maturation cleavage of a capsid protein precursor locks the virus in a metastable state, and the receptor acts like a transition-state catalyst to overcome an energy barrier and release the mature virion from the metastable state. This initiates a series of conformational changes that allow the virus to attach to membranes, form a pore, and finally release its RNA genome into the cytoplasm. This model has striking parallels with emerging models for the maturation and cell entry of more complex enveloped viruses such as influenza virus and HIV.
-
-
-
Prions as Protein-Based Genetic Elements
Vol. 56 (2002), pp. 703–741More Less▪ AbstractFungal prions are fascinating protein-based genetic elements. They alter cellular phenotypes through self-perpetuating changes in protein conformation and are cytoplasmically partitioned from mother cell to daughter. The four prions of Saccharomyces cerevisiae and Podospora anserina affect diverse biological processes: translational termination, nitrogen regulation, inducibility of other prions, and heterokaryon incompatibility. They share many attributes, including unusual genetic behaviors, that establish criteria to identify new prions. Indeed, other fungal traits that baffled microbiologists meet some of these criteria and might be caused by prions. Recent research has provided notable insight about how prions are induced and propagated and their many biological roles. The ability to become a prion appears to be evolutionarily conserved in two cases. [PSI+] provides a mechanism for genetic variation and phenotypic diversity in response to changing environments. All available evidence suggests that prions epigenetically modulate a wide variety of fundamental biological processes, and many await discovery.
-
-
-
Mechanisms of Solvent Tolerance in Gram-Negative Bacteria
Vol. 56 (2002), pp. 743–768More Less▪ AbstractOrganic solvents can be toxic to microorganisms, depending on the inherent toxicity of the solvent and the intrinsic tolerance of the bacterial species and strains. The toxicity of a given solvent correlates with the logarithm of its partition coefficient in n-octanol and water (log Pow). Organic solvents with a log Pow between 1.5 and 4.0 are extremely toxic for microorganisms and other living cells because they partition preferentially in the cytoplasmic membrane, disorganizing its structure and impairing vital functions. Several possible mechanisms leading to solvent-tolerance in gram-negative bacteria have been proposed: (a) adaptive alterations of the membrane fatty acids and phospholipid headgroup composition, (b) formation of vesicles loaded with toxic compounds, and (c) energy-dependent active efflux pumps belonging to the resistance-nodulation–cell division (RND) family, which export toxic organic solvents to the external medium. In these mechanisms, changes in the phospholipid profile and extrusion of the solvents seem to be shared by different strains. The most significant changes in phospholipids are an increase in the melting temperature of the membranes by rapid cis-to-trans isomerization of unsaturated fatty acids and modifications in the phospholipid headgroups. Toluene efflux pumps are involved in solvent tolerance in several gram-negative strains, e.g., Escherichia coli, Pseudomonas putida, and Pseudomonas aeruginosa. The AcrAB-TolC and AcrEF-TolC efflux pumps are important for n-hexane tolerance in E. coli. A number of P. putida strains have been isolated that tolerate toxic hydrocarbons such as toluene, styrene, and p-xylene. At least three efflux pumps (TtgABC, TtgDEF, and TtgGHI) are present in the most extensively characterized solvent-tolerant strain, P. putida DOT-T1E, and the number of efflux pumps has been found to correlate with the degree of solvent tolerance in different P. putida strains. The operation of these efflux pumps seems to be coupled to the proton motive force via the TonB system, although the intimate mechanism of energy transfer remains elusive. Specific and global regulators control the expression of the efflux pump operons of E. coli and P. putida at the transcriptional level.
-
-
-
Growing Old: Metabolic Control and Yeast Aging
Vol. 56 (2002), pp. 769–792More Less▪ AbstractThe metabolic characteristics of a yeast cell determine its life span. Depending on conditions, stress resistance can have either a salutary or a deleterious effect on longevity. Gene dysregulation increases with age, and countering it increases life span. These three determinants of yeast longevity may be interrelated, and they are joined by a potential fourth, genetic stability. These factors can also operate in phylogenetically diverse species. Adult longevity seems to borrow features from the genetic programs of dormancy to provide the metabolic and stress resistance resources necessary for extended survival. Both compensatory and preventive mechanisms determine life span, while epigenetic factors and the element of chance contribute to the role that genes and environment play in aging.
-
Previous Volumes
-
Volume 78 (2024)
-
Volume 77 (2023)
-
Volume 76 (2022)
-
Volume 75 (2021)
-
Volume 74 (2020)
-
Volume 73 (2019)
-
Volume 72 (2018)
-
Volume 71 (2017)
-
Volume 70 (2016)
-
Volume 69 (2015)
-
Volume 68 (2014)
-
Volume 67 (2013)
-
Volume 66 (2012)
-
Volume 65 (2011)
-
Volume 64 (2010)
-
Volume 63 (2009)
-
Volume 62 (2008)
-
Volume 61 (2007)
-
Volume 60 (2006)
-
Volume 59 (2005)
-
Volume 58 (2004)
-
Volume 57 (2003)
-
Volume 56 (2002)
-
Volume 55 (2001)
-
Volume 54 (2000)
-
Volume 53 (1999)
-
Volume 52 (1998)
-
Volume 51 (1997)
-
Volume 50 (1996)
-
Volume 49 (1995)
-
Volume 48 (1994)
-
Volume 47 (1993)
-
Volume 46 (1992)
-
Volume 45 (1991)
-
Volume 44 (1990)
-
Volume 43 (1989)
-
Volume 42 (1988)
-
Volume 41 (1987)
-
Volume 40 (1986)
-
Volume 39 (1985)
-
Volume 38 (1984)
-
Volume 37 (1983)
-
Volume 36 (1982)
-
Volume 35 (1981)
-
Volume 34 (1980)
-
Volume 33 (1979)
-
Volume 32 (1978)
-
Volume 31 (1977)
-
Volume 30 (1976)
-
Volume 29 (1975)
-
Volume 28 (1974)
-
Volume 27 (1973)
-
Volume 26 (1972)
-
Volume 25 (1971)
-
Volume 24 (1970)
-
Volume 23 (1969)
-
Volume 22 (1968)
-
Volume 21 (1967)
-
Volume 20 (1966)
-
Volume 19 (1965)
-
Volume 18 (1964)
-
Volume 17 (1963)
-
Volume 16 (1962)
-
Volume 15 (1961)
-
Volume 14 (1960)
-
Volume 13 (1959)
-
Volume 12 (1958)
-
Volume 11 (1957)
-
Volume 10 (1956)
-
Volume 9 (1955)
-
Volume 8 (1954)
-
Volume 7 (1953)
-
Volume 6 (1952)
-
Volume 5 (1951)
-
Volume 4 (1950)
-
Volume 3 (1949)
-
Volume 2 (1948)
-
Volume 1 (1947)
-
Volume 0 (1932)