Showing papers by "Hungarian Academy of Sciences published in 2009"

Alien species in a warmer world: risks and opportunities

Abstract: Climate change and biological invasions are key processes affecting global biodiversity, yet their effects have usually been considered separately. Here, we emphasise that global warming has enabled alien species to expand into regions in which they previously could not survive and reproduce. Based on a review of climate-mediated biological invasions of plants, invertebrates, fishes and birds, we discuss the ways in which climate change influences biological invasions. We emphasise the role of alien species in a more dynamic context of shifting species' ranges and changing communities. Under these circumstances, management practices regarding the occurrence of 'new' species could range from complete eradication to tolerance and even consideration of the 'new' species as an enrichment of local biodiversity and key elements to maintain ecosystem services.

Molecular evolution of a novel hyperactive Sleeping Beauty transposase enables robust stable gene transfer in vertebrates

Abstract: The Sleeping Beauty (SB) transposon is a promising technology platform for gene transfer in vertebrates; however, its efficiency of gene insertion can be a bottleneck in primary cell types. A large-scale genetic screen in mammalian cells yielded a hyperactive transposase (SB100X) with approximately 100-fold enhancement in efficiency when compared to the first-generation transposase. SB100X supported 35-50% stable gene transfer in human CD34(+) cells enriched in hematopoietic stem or progenitor cells. Transplantation of gene-marked CD34(+) cells in immunodeficient mice resulted in long-term engraftment and hematopoietic reconstitution. In addition, SB100X supported sustained (>1 year) expression of physiological levels of factor IX upon transposition in the mouse liver in vivo. Finally, SB100X reproducibly resulted in 45% stable transgenesis frequencies by pronuclear microinjection into mouse zygotes. The newly developed transposase yields unprecedented stable gene transfer efficiencies following nonviral gene delivery that compare favorably to stable transduction efficiencies with integrating viral vectors and is expected to facilitate widespread applications in functional genomics and gene therapy.

ANCHOR: web server for predicting protein binding regions in disordered proteins.

Abstract: Summary: ANCHOR is a web-based implementation of an original method that takes a single amino acid sequence as an input and predicts protein binding regions that are disordered in isolation but can undergo disorder-to-order transition upon binding. The server incorporates the result of a general disorder prediction method, IUPred and can carry out simple motif searches as well. Availability: The web server is available at http://anchor.enzim.hu. The program package is freely available for academic users. Contact: zsuzsa@enzim.hu

Amyloid β-Induced Neuronal Hyperexcitability Triggers Progressive Epilepsy

Abstract: Alzheimer's disease is associated with an increased risk of unprovoked seizures. However, the underlying mechanisms of seizure induction remain elusive. Here, we performed video-EEG recordings in mice carrying mutant human APPswe and PS1dE9 genes (APdE9 mice) and their wild-type littermates to determine the prevalence of unprovoked seizures. In two recording episodes at the onset of amyloid beta (Abeta) pathogenesis (3 and 4.5 months of age), at least one unprovoked seizure was detected in 65% of APdE9 mice, of which 46% had multiple seizures and 38% had a generalized seizure. None of the wild-type mice had seizures. In a subset of APdE9 mice, seizure phenotype was associated with a loss of calbindin-D28k immunoreactivity in dentate granular cells and ectopic expression of neuropeptide Y in mossy fibers. In APdE9 mice, persistently decreased resting membrane potential in neocortical layer 2/3 pyramidal cells and dentate granule cells underpinned increased network excitability as identified by patch-clamp electrophysiology. At stimulus strengths evoking single-component EPSPs in wild-type littermates, APdE9 mice exhibited decreased action potential threshold and burst firing of pyramidal cells. Bath application (1 h) of Abeta1-42 or Abeta25-35 (proto-)fibrils but not oligomers induced significant membrane depolarization of pyramidal cells and increased the activity of excitatory cell populations as measured by extracellular field recordings in the juvenile rodent brain, confirming the pathogenic significance of bath-applied Abeta (proto-)fibrils. Overall, these data identify fibrillar Abeta as a pathogenic entity powerfully altering neuronal membrane properties such that hyperexcitability of pyramidal cells culminates in epileptiform activity.

Prediction of Protein Binding Regions in Disordered Proteins

Abstract: Many disordered proteins function via binding to a structured partner and undergo a disorder-to-order transition. The coupled folding and binding can confer several functional advantages such as the precise control of binding specificity without increased affinity. Additionally, the inherent flexibility allows the binding site to adopt various conformations and to bind to multiple partners. These features explain the prevalence of such binding elements in signaling and regulatory processes. In this work, we report ANCHOR, a method for the prediction of disordered binding regions. ANCHOR relies on the pairwise energy estimation approach that is the basis of IUPred, a previous general disorder prediction method. In order to predict disordered binding regions, we seek to identify segments that are in disordered regions, cannot form enough favorable intrachain interactions to fold on their own, and are likely to gain stabilizing energy by interacting with a globular protein partner. The performance of ANCHOR was found to be largely independent from the amino acid composition and adopted secondary structure. Longer binding sites generally were predicted to be segmented, in agreement with available experimentally characterized examples. Scanning several hundred proteomes showed that the occurrence of disordered binding sites increased with the complexity of the organisms even compared to disordered regions in general. Furthermore, the length distribution of binding sites was different from disordered protein regions in general and was dominated by shorter segments. These results underline the importance of disordered proteins and protein segments in establishing new binding regions. Due to their specific biophysical properties, disordered binding sites generally carry a robust sequence signal, and this signal is efficiently captured by our method. Through its generality, ANCHOR opens new ways to study the essential functional sites of disordered proteins.

Newborn infants detect the beat in music

Abstract: To shed light on how humans can learn to understand music, we need to discover what the perceptual capabilities with which infants are born. Beat induction, the detection of a regular pulse in an auditory signal, is considered a fundamental human trait that, arguably, played a decisive role in the origin of music. Theorists are divided on the issue whether this ability is innate or learned. We show that newborn infants develop expectation for the onset of rhythmic cycles (the downbeat), even when it is not marked by stress or other distinguishing spectral features. Omitting the downbeat elicits brain activity associated with violating sensory expectations. Thus, our results strongly support the view that beat perception is innate.

A theorem of finite sets

Abstract: HAJNAL proved this statement in the case of l = 3 (unpublished). In this paper I prove for all cases that this is, indeed, the minimum, and find the (more complicated) minimum also for arbitrary n. The theorem is probably useful in proofs by induction over the maximal number of elements of the subsets in a system, as was SPERNER’S, lemma in his paper [1].

Vitamin C: update on physiology and pharmacology

Abstract: Although ascorbic acid is an important water-soluble antioxidant and enzyme cofactor in plants and animals, humans and some other species do not synthesize ascorbate due to the lack of the enzyme catalyzing the final step of the biosynthetic pathway, and for them it has become a vitamin. This review focuses on the role of ascorbate in various hydroxylation reactions and in the redox homeostasis of subcellular compartments including mitochondria and endoplasmic reticulum. Recently discovered functions of ascorbate in nucleic acid and histone dealkylation and proteoglycan deglycanation are also summarized. These new findings might delineate a role for ascorbate in the modulation of both pro- and anti-carcinogenic mechanisms. Recent advances and perspectives in therapeutic applications are also reviewed. On the basis of new and earlier observations, the advantages of the lost ability to synthesize ascorbate are pondered. The increasing knowledge of the functions of ascorbate and of its molecular sites of action can mechanistically substantiate a place for ascorbate in the treatment of various diseases.

The major inflammatory mediator interleukin-6 and obesity

Abstract: Adipose tissue is one of the main sources of inflammatory mediators, with interleukin-6 (IL-6) among them Although high systemic levels of inflammatory mediators are cachectogenic and/or anorexic, today it is a widely propagated thesis that in the background of obesity, a low level of chronic inflammation can be found, with IL-6 being one of the many suggested mediators This paper reviews the studies describing elevated IL-6 levels in obese patients and the role of adipocytes and adipose-tissue macrophages in the production of IL-6 The secretion of IL-6 is regulated by several physiologic or pathologic factors: hormones, cytokines, diet, physical activity, stress, hypoxia, and others Adipose tissue-derived IL-6 may have an effect on metabolism through several mechanisms, including adipose tissue-specific gene expression, triglyceride release, lipoprotein lipase downregulation, insulin sensitivity, and so on Having a better understanding of these mechanisms may contribute to the prevention and treatment of obesity

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales

Abstract: In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.

Quasi-Local Energy-Momentum and Angular Momentum in General Relativity.

Abstract: The present status of the quasi-local mass, energy-momentum and angular-momentum constructions in general relativity is reviewed. First, the general ideas, concepts, and strategies, as well as the necessary tools to construct and analyze the quasi-local quantities, are recalled. Then, the various specific constructions and their properties (both successes and deficiencies are discussed. Finally, some of the (actual and potential) applications of the quasi-local concepts and specific constructions are briefly mentioned.

Glutathione as an Antioxidant and Regulatory Molecule in Plants Under Abiotic Stress Conditions

Abstract: The glutathione (GSH)/glutathione disulfide (GSSG) redox couple is involved in several physiologic processes in plants under both optimal and stress conditions. It participates in the maintenance of redox homeostasis in the cells. The redox state of the GSH/GSSG couple is defined by its reducing capacity and the half-cell reduction potential, and differs in the various organs, tissues, cells, and compartments, changing during the growth and development of the plants. When characterizing this redox couple, the synthesis, degradation, oxidation, and transport of GSH and its conjugation with the sulfhydryl groups of other compounds should be considered. Under optimal growth conditions, the high GSH/GSSG ratio results in a reducing environment in the cells which maintains the appropriate structure and activity of protein molecules because of the inhibition of the formation of intermolecular disulfide bridges. In response to abiotic stresses, the GSH/GSSG ratio decreases due to the oxidation of GSH during the detoxification of reactive oxygen species (ROS) and changes in its metabolism. The lower GSH/GSSG ratio activates various defense mechanisms through a redox signalling pathway, which includes several oxidants, antioxidants, and stress hormones. In addition, GSH may control gene expression and the activity of proteins through glutathionylation and thiol-disulfide conversion. This review discusses the size and redox state of the GSH pool, including their regulation, their role in redox signalling and defense processes, and the changes caused by abiotic stress.

The Human K-Complex Represents an Isolated Cortical Down-State

Abstract: The electroencephalogram (EEG) is a mainstay of clinical neurology and is tightly correlated with brain function, but the specific currents generating human EEG elements remain poorly specified because of a lack of microphysiological recordings. The largest event in healthy human EEGs is the K-complex (KC), which occurs in slow-wave sleep. Here, we show that KCs are generated in widespread cortical areas by outward dendritic currents in the middle and upper cortical layers, accompanied by decreased broadband EEG power and decreased neuronal firing, which demonstrate a steep decline in network activity. Thus, KCs are isolated “down-states,” a fundamental cortico-thalamic processing mode already characterized in animals. This correspondence is compatible with proposed contributions of the KC to sleep preservation and memory consolidation.

Regulation of cortical microcircuits by unitary GABA-mediated volume transmission

Abstract: Many receptors for neurotransmitters are found outside neuronal synapses and can be activated by excess neurotransmitter spilling out of the synaptic cleft. But neurotransmitter reuptake by extrasynaptic transporters has been thought to limit the significance of such extrasynaptic signals. Now Tamas and colleagues show that a poorly described cell type of the cerebral cortex, the neurogliaform cells, release the inhibitory neurotransmitter GABA as a large and dense cloud and thus do not require synapses to produce inhibitory responses in the vast majority of neighbouring neurons. They further show that neurosteroids suppress these neurogliaform cells' excitability, which may explain the role of these hormones in post-partum depression and premenstrual syndrome. Excess neurotransmitter diffuses out of the synaptic cleft, where it can activate neurotransmitter receptors outside the postsynaptic density. However, neurotransmitter reuptake is thought to limit the significance of such extrasynaptic, or 'volume', transmission. Individual neurogliaform cells are now shown to release enough GABA for volume transmission within the axonal cloud; these cells do not require synapses to produce inhibitory responses in nearby neurons. GABA (γ-aminobutyric acid) is predominantly released by local interneurons in the cerebral cortex to particular subcellular domains of the target cells1,2. This suggests that compartmentalized, synapse-specific action of GABA is required in cortical networks for phasic inhibition2,3,4. However, GABA released at the synaptic cleft diffuses to receptors outside the postsynaptic density and thus tonically activates extrasynaptic GABAA and GABAB receptors, which include subtypes of both receptor families especially sensitive to low concentrations of GABA3,4,5,6,7. The synaptic and extrasynaptic action of GABA corroborates the idea that neurons of the brain use synaptic (or wiring) transmission and non-synaptic (or volume) transmission for communication8,9. However, re-uptake mechanisms restrict the spatial extent of extrasynaptic GABA-mediated effects10,11, and it has been proposed that the concerted action of several presynaptic interneurons, the sustained firing of individual cells or an increase in release-site density is required to reach ambient GABA levels sufficient to activate extrasynaptic receptors4,9,11,12,13. Here we show that individual neurogliaform cells release enough GABA for volume transmission within the axonal cloud and, thus, that neurogliaform cells do not require synapses to produce inhibitory responses in the overwhelming majority of nearby neurons. Neurogliaform cells suppress connections between other neurons acting on presynaptic terminals that do not receive synapses at all in the cerebral cortex. They also reach extrasynaptic, δ-subunit-containing GABAA (GABAAδ) receptors responsible for tonic inhibition. We show that GABAAδ receptors are localized to neurogliaform cells preferentially among cortical interneurons. Neurosteroids, which are modulators of GABAAδ receptors, alter unitary GABA-mediated effects between neurogliaform cells. In contrast to the specifically placed synapses formed by other interneurons, the output of neurosteroid-sensitive neurogliaform cells represents the ultimate form of the lack of spatial specificity in GABA-mediated systems, leading to long-lasting network hyperpolarization combined with widespread suppression of communication in the local circuit.

Adult generation of glutamatergic olfactory bulb interneurons

Abstract: The adult mouse subependymal zone (SEZ) harbors neural stem cells that are thought to exclusively generate GABAergic interneurons of the olfactory bulb. We examined the adult generation of glutamatergic juxtaglomerular neurons, which had dendritic arborizations that projected into adjacent glomeruli, identifying them as short-axon cells. Fate mapping revealed that these originate from Neurog2- and Tbr2-expressing progenitors located in the dorsal region of the SEZ. Examination of the progenitors of these glutamatergic interneurons allowed us to determine the sequential expression of transcription factors in these cells that are thought to be hallmarks of glutamatergic neurogenesis in the developing cerebral cortex and adult hippocampus. Indeed, the molecular specification of these SEZ progenitors allowed for their recruitment into the cerebral cortex after a lesion was induced. Taken together, our data indicate that SEZ progenitors not only produce a population of adult-born glutamatergic juxtaglomerular neurons, but may also provide a previously unknown source of progenitors for endogenous repair.

GABAergic Neurons of the Medial Septum Lead the Hippocampal Network during Theta Activity

Abstract: Information processing in the hippocampus critically relies on its reciprocal interaction with the medial septum (MS). Synchronization of the septo-hippocampal system was demonstrated during both major hippocampal activity states, the regular theta rhythm and the large amplitude irregular activity. Previous experimental and modeling data suggest that the MS provides rhythmic drive to the hippocampus, and hippocampo-septal feedback synchronizes septal pacemaker units. However, this view has recently been questioned based on the possibility of intrahippocampal theta genesis. Previously, we identified putative pacemaker neurons expressing parvalbumin (PV) and/or the pacemaker hyperpolarization-activated and cyclic nucleotide-gated nonselective cation channel (HCN) in the MS. In this study, by analyzing the temporal relationship of activity between the PV/HCN-containing medial septal neurons and hippocampal local field potential, we aimed to uncover whether the sequence of events during theta formation supports the classic view of septal drive or the challenging theory of hippocampal pacing of theta. Importantly, by implementing a circular statistical method, a temporal lead of these septal neurons over the hippocampus was observed on the course of theta synchronization. Moreover, the activity of putative hippocampal interneurons also preceded hippocampal local field theta, but by a shorter time period compared with PV/HCN-containing septal neurons. Using the concept of mutual information, the action potential series of PV/HCN-containing neurons shared higher amount of information with hippocampal field oscillation than PV/HCN-immunonegative cells. Thus, a pacemaker neuron population of the MS leads hippocampal activity, presumably via the synchronization of hippocampal interneurons.

Rotavirus disease and vaccination: impact on genotype diversity.

Abstract: Temporal and spatial fluctuations in the genotype distribution of human rotaviruses are continuously observed in surveillance studies. New genotypes, such as G9 and G12, have emerged and spread worldwide in a very short time span. In addition, reassortment events have the potential to contribute substantially to genetic diversity among human and animal rotaviruses. With the recent introduction of the two rotavirus vaccines, RotaTeq and Rotarix, in many countries, it appears that the total number of hospitalizations due to rotavirus infections is being reduced, at least in developed countries that implemented a universal immunization program. However, continued surveillance is warranted, especially regarding the long-term effects of the vaccines. No data analyses are available to clarify whether rotavirus vaccine introduction would allow other rotavirus P and G genotypes, which are not covered by the current vaccines, to emerge into the human population and fill the apparent gap. This kind of data analysis is essential, but its interpretation is hampered by natural and cyclical genotype fluctuations.

Mutation discovery for crop improvement

Abstract: Increasing crop yields to ensure food security is a major challenge. Mutagenesis is an important tool in crop improvement and is free of the regulatory restrictions imposed on genetically modified organisms. The forward genetic approach enables the identification of improved or novel phenotypes that can be exploited in conventional breeding programmes. Powerful reverse genetic strategies that allow the detection of induced point mutations in individuals of the mutagenized populations can address the major challenge of linking sequence information to the biological function of genes and can also identify novel variation for plant breeding. This review briefly discusses recent advances in the detection of mutants and the potential of mutagenesis for crop improvement.

Transposon-mediated genome manipulation in vertebrates.

Abstract: Transposable elements are DNA segments with the unique ability to move about in the genome. This inherent feature can be exploited to harness these elements as gene vectors for genome manipulation. Transposon-based genetic strategies have been established in vertebrate species over the last decade, and current progress in this field suggests that transposable elements will serve as indispensable tools. In particular, transposons can be applied as vectors for somatic and germline transgenesis, and as insertional mutagens in both loss-of-function and gain-of-function forward mutagenesis screens. In addition, transposons will gain importance in future cell-based clinical applications, including nonviral gene transfer into stem cells and the rapidly developing field of induced pluripotent stem cells. Here we provide an overview of transposon-based methods used in vertebrate model organisms with an emphasis on the mouse system and highlight the most important considerations concerning genetic applications of the transposon systems.

Structure and Function of Intrinsically Disordered Proteins

Abstract: Principles of Protein Structure and Function Physical Forces That Shape Protein Structure Primary Structure: Amino Acid Sequence Protein-Coding Genes Post-Translational Modifications of Amino Acids Hierarchical Description of Structure Folding of a Protein Unfolding of a Protein: Lessons from Polymer Theory The Limits of Global Descriptions of the Unfolded State Databases of Proteins and Protein Structures DisProt: The Database of Disordered Proteins The Classical Structure-Function Paradigm A Brief History of Protein Disorder Can We Define Disorder? The History of Disorder So We Have Disordered Proteins Indirect Techniques for Recognizing and Characterizing Protein Disorder Resistance to Heat Resistance to Chemical Denaturation Unusual SDS-PAGE Mobility Enhanced Proteolytic Sensitivity Limited Proteolysis and Local Structure Differential Scanning Calorimetry Isothermal Titration Calorimetry Chemical Cross-Linking H/D Exchange Hydrodynamic Techniques Gel Filtration (Size-Exclusion) Chromatography Dynamic Light Scattering Analytical Ultracentrifugation Small-Angle X-Ray Scattering Pulsed-Field Gradient NMR Spectroscopic Techniques for Characterizing Disorder X-Ray Crystallography Fluorescence Spectroscopy Fourier-Transform Infrared Resonance Spectroscopy Circular Dichroism Raman Optical Activity Spectroscopy Electron Paramagnetic Resonance Spectroscopy Electron Microscopy Atomic Force Microscopy Nuclear Magnetic Resonance Basic Principles Global Characterization by NMR Sequence-Specific Structural Information Special Applications Proteomic Approaches for the Identification of IDPs Expectations and Limitations of Proteomic Studies 2DE-MS Identification of Proteins in Extracts Enriched for Disorder Native/Urea 2DE Provides Direct Information on Disorder IDPs under Conditions Approaching In Vivo Macromolecular Crowding in the Cell In Vitro Approaches to Mimicking Crowding Conditions The State of IDPs In Vivo Physiological Half-Life of IDPs: No Signs of Rapid Degradation Indirect Considerations Underscoring Disorder of IDPs In Vivo Prediction of Disorder General Points Propensity-Based Predictors Machine-Learning Algorithms Prediction Based on Interresidue Contacts Prediction of Short and Long Regions of Disorder Separately Combination of Predictors: Meta-Servers Prediction of Functional Motifs in IDPs Comparison of the Accuracy of Predictors: The CASP Experiment A Better Target Prioritization in Structural Genomics Structure of IDPs Primary Structure of Disordered Proteins Secondary Structure of Disordered Proteins Ambiguity in Structure Tertiary Structure: Global Features of IDP Structures Dynamics of IDP Structure: The Time-Course of Fluctuations within the Ensemble A Readout of Structure: The Hydrate Layer of IDPs Biological Processes Enriched in Disorder Biological Functions Enriched with Disorder Disorder in Transcription/Transcription Regulation Disorder in Signaling Proteins Nucleic Acid-Containing Organelles Disorder in RNA-Binding Proteins: Transcription and RNA Folding Cytoskeletal Proteins Disorder in Stress Proteins Disorder and Metal Binding Disorder and Enzyme Activity Is There a Link between the Pattern of Disorder and Function? Molecular Functions of Disordered Proteins Entropic Chain Functions Display Site Functions Chaperone Functions Effector Functions Scavenger Functions Assembler Functions Prion Functions Evolution and Prevalence of Disorder Phylogenetic Distribution of Disorder Fast Evolution of IDPs by Point Mutations Fast Evolution of IDPs by Repeat Expansion Fast Evolution and Functionality of Disordered Proteins Structural Variability and Evolvability of New Functions Extension of the Structure-Function Paradigm Functions That Stem Directly from the Disordered State Recognition Functions: Recognition by Short Motifs Disorder-to-Order Transition in Recognition: Mechanistic and Thermodynamic Aspects Recognition Functions: Uncoupling Specificity from Binding Strength Implications of Disorder for the Kinetics of Interactions Adaptability and Moonlighting Nested Interfaces Disorder in the Bound State: Fuzziness Processivity of Binding Sequence Independence in Recognition Ultrasensitivity of Recognition Signal Propagation in the Structural Ensemble of IDPs Disorder and Alternative Splicing Molecular Mimicry by a Disordered Region Entropy Transfer in Chaperone Action Structural Disorder and Disease Structural Disorder and Cancer Structural Disorder in Proteins Involved in Cardiovascular Diseases, Diabetes, and Autoimmune Diseases Structural Disorder and Neurodegenerative Diseases Systemic Amyloidoses Common Themes in Amyloid Formation Does Structural Disorder Pose a Danger? Disorder in Pathogenic Organisms Rational Drug Design Based on Protein Disorder References

Bacterial growth and motility in sub-micron constrictions

Abstract: In many naturally occurring habitats, bacteria live in micrometer-size confined spaces. Although bacterial growth and motility in such constrictions is of great interest to fields as varied as soil microbiology, water purification, and biomedical research, quantitative studies of the effects of confinement on bacteria have been limited. Here, we establish how Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria can grow, move, and penetrate very narrow constrictions with a size comparable to or even smaller than their diameter. We show that peritrichously flagellated E. coli and B. subtilis are still motile in microfabricated channels where the width of the channel exceeds their diameters only marginally (∼30%). For smaller widths, the motility vanishes but bacteria can still pass through these channels by growth and division. We observe E. coli, but not B. subtilis, to penetrate channels with a width that is smaller than their diameter by a factor of approximately 2. Within these channels, bacteria are considerably squeezed but they still grow and divide. After exiting the channels, E. coli bacteria obtain a variety of anomalous cell shapes. Our results reveal that sub-micron size pores and cavities are unexpectedly prolific bacterial habitats where bacteria exhibit morphological adaptations.