Annual review of microbiology最新文献

Helicobacter pylori is a motile bacterium that uses its high-torque flagella to colonize the diverse and challenging landscapes within the human stomach. H. pylori flagella possess numerous variations from canonical systems in motor dimensions, stator occupancy, flagellin composition, and the incorporation of additional basal body elements. Many, but not all, of these variations have been identified and characterized. H. pylori flagellar gene transcriptional regulation diverges from that of canonical models in its lack of a single master regulator, reliance on a hierarchy based on two σ factors, and use of a distributed set of regulatory checkpoints. Emerging evidence suggests H. pylori flagella play roles in mechanosensing and regulating the motile-sessile transition, relying on flagellar cage protein homologs of the type 4 pili PilO, PilN, and PilM and operating independently of c-di-GMP. The study of H. pylori flagella has revealed many surprises, and more surprises certainly await in this exciting field.

The asaccharolytic anaerobe Porphyromonas gingivalis is a contextually virulent keystone pathogen in the onset and progression of periodontal diseases. P. gingivalis is equipped with an array of virulence factors that promote oral colonization and adaptation to the prevailing heme and oxygen levels in the periodontal ecosystem. Interactions among the oral polymicrobial community lead to increased nososymbiocity (community pathogenicity), and P. gingivalis is adept at inducing dysbiotic inflammatory responses. In particular, the decoupling of inflammation from bacterial killing mechanisms misdirects innate immunity and provides proteinaceous metabolic substrates. The properties that underlie the success of P. gingivalis also provide the framework for its versatility as a systemic pathogen. P. gingivalis can exert a systemic influence following, for example, hematogenous spread and localization at remote tissues. Additionally, secreted bioactive components and metabolites, as well as locally generated immune effectors, have the potential to disrupt homeostasis on a systemic level. The ability to subvert epithelial cell life-and-death decisions further endows P. gingivalis with oncopathogenic properties. In this review, we first examine polymicrobial synergy, colonization, and metabolic adaptation in the periodontal niche; then analyze mechanisms of immune subversion at epithelial and myeloid interfaces; and finally discuss how these strategies contribute to periodontitis and to systemic inflammatory, autoimmune, neurodegenerative, and neoplastic diseases.

Treponema pallidum subsp. pallidum is the causative agent of syphilis, a chronic and potentially devastating infection that is resurging globally. The bacterium is highly invasive, disseminates rapidly, and establishes decades-long latency that may progress to severe tissue destruction and death. T. pallidum's reduced genome contributes to its dependence on the host. Its impressive TprK antigenic variation, scarce outer membrane proteins, and periplasmic flagella provide for immune evasion, enabling persistence and reinfection. Our understanding of syphilis pathogenesis derives largely from experimental infection in rabbits and from historical studies in humans, though recent advances in continuous cultivation, genetic manipulation, hybrid-capture genome sequencing, and multi-omic approaches have opened new avenues for dissecting host-pathogen interactions and disease pathogenesis. This review highlights mechanisms of syphilis pathogenesis, the central role of the immune response in disease causation and progression, and the role of new technologies in answering long-standing questions and informing vaccine development.

Microsporidia are fungal intracellular parasites of animals and are a threat to human health and food security. In 2001, they became the first eukaryotic parasites to have their genome fully sequenced. Analysis revealed they possessed the smallest eukaryotic genomes, having undergone extreme genomic reduction. In this article, we review how genomic technologies have been applied to these parasites since this seminal discovery. We demonstrate how additional microsporidian genomes have enabled the examination of genome structure, gene conservation, population genetics, and diversity. We describe how transcriptomics has revealed parasite gene regulation across different life stages and host responses to infection. We discuss how proteomic and structural techniques have advanced our understanding of microsporidian biology and how various approaches have elucidated microsporidian protein function. Finally, we explore future directions for applying genomic technologies to accelerate our understanding of these fascinating parasites.

Bdellovibrio bacteriovorus represents one of nature's most remarkable examples of obligate bacterial predation. This small, highly motile bacterium exhibits a biphasic life cycle alternating between a free-swimming attack phase and an intraperiplasmic growth phase within gram-negative prey bacteria. Recent advances have elucidated the molecular machinery coordinating prey recognition, invasion, and host manipulation, revealing sophisticated enzymatic arsenals and regulatory networks that orchestrate the predatory program. Transcriptomic studies demonstrate precise temporal control of lytic enzymes, nutrient acquisition systems, and developmental checkpoints throughout the life cycle. Bdellovibrio and related organisms occupy diverse niches, including soil, freshwater, and the mammalian gut, where they influence bacterial community composition through top-down predation. This ecological ubiquity, combined with inherent bactericidal activity, has generated considerable interest in therapeutic applications against multidrug-resistant pathogens, with encouraging results in animal infection models. In this article, we synthesize current understanding of predatory mechanisms, environmental roles, and biotechnological potential of Bdellovibrio while identifying key knowledge gaps: the regulatory logic governing life cycle transitions, molecular determinants of host range, and predator-prey population dynamics. Addressing these questions will advance both fundamental microbiology and antimicrobial innovation.

In a process known as phenotypic heterogeneity or phenotypic variation, bacteria can produce distinct phenotypes within an isogenic population in response to shifting environmental conditions. Noise in gene expression, asymmetric cell division, phase variation, and quorum sensing are some of the mechanisms that contribute to this variability, which is maintained by gene regulatory networks (usually involving feedback loops). Bistability in gene regulatory networks generates subpopulations exhibiting specific traits that can contribute to more complex adaptive strategies, promoting the fitness of the bacterial community as a whole. This review explores recent examples of phenotypic heterogeneity and its functional importance in bacterial collective behaviors. We focus on how synthetic biology can be used to better understand bacterial gene regulatory networks and the mechanisms underlying antibiotic resilience and persistence, and we discuss the bistability of integrative and conjugative elements.

Malaria, a life-threatening disease caused by eukaryotic intracellular parasites belonging to the genus Plasmodium, is classically characterized by the infection of circulating red blood cells. However, growing evidence reveals that these parasites also accumulate within the bone marrow, the primary site of red cell production. In this review, we detail the evidence for this cryptic reservoir of parasites, the associated implications for host erythropoiesis, and an array of complex host responses elicited by the parasites in this niche. The underlying bone marrow pathology stems from multiple factors, including direct parasite invasion of erythroid precursor cells and inflammatory effects of parasite-derived factors. By consolidating current evidence on this dynamic interaction, this review highlights critical questions for future research into the mechanisms of ineffective erythropoiesis and the development of host-protective therapeutic strategies.

Structural maintenance of chromosomes (SMC) complexes are conserved ATP-driven machines that organize, compact, and segregate genomes in all domains of life. Despite variation in subunit composition and regulation, all SMC complexes share a core structure and mechanism of action. Bacteria possess two major classes of SMC complexes, SMC-ScpAB and MukBEF, which function in chromosome compaction and segregation. In addition, some bacteria contain other SMC complexes or SMC-like systems such as MksBEF, Wadjet, RecN, and SbcC, each with specialized functions. Bacterial SMC complexes coordinate genome maintenance, DNA replication, DNA repair, plasmid defense, and cell physiology. In this review, we discuss the structure and function of these bacterial SMC complexes, highlighting the shared characteristics and unique strategies employed by each.

The mycobacterial cell envelope is a formidable barrier, regarded as one of the most chemically and structurally elaborate architectures in the Bacteria kingdom. Membrane remodeling, defined as changes in membrane lipid composition in response to stressors, has been a subject of broad investigation because of its implications for permeability, antibiotic susceptibility, immunogenicity, and virulence. However, because remodeling is a highly dynamic process governed by multiple, deeply interconnected cellular response pathways, its underlying mechanisms and biophysical consequences remain incompletely understood. In this review, we synthesize the current knowledge of how the composition and organization of membrane lipids shift under physiologically relevant conditions, and we examine how these changes intersect with key stress response pathways. As a unifying thread connecting lipid composition, envelope architecture, and cellular function, we summarize our understanding of mycobacterial membrane biophysical properties, highlighting recent advances as well as conceptual and methodological gaps that remain in the field.

Quorum sensing (QS) enables bacteria to coordinate collective behaviors in response to population density. LuxI/R QS systems, common among gram-negative bacteria, consist of a LuxI-type synthase that produces an N-acyl L-homoserine lactone (AHL) signaling molecule and a LuxR-type receptor that senses the AHL. At threshold AHL concentrations, LuxR-type receptors undergo ligand-induced conformational changes that affect DNA binding and target gene transcription. Because of their role in regulating myriad collective behaviors, LuxI/R systems are targets for many applications, including antivirulence strategies and the engineering of beneficial microbiomes. Recent structural studies have led to substantial progress in understanding molecular mechanisms of LuxI/R systems. However, LuxR-type receptors fall into functionally diverse subfamilies for which structural bases remain incompletely understood. In this article, we summarize recent structural and mechanistic insights into LuxR-type receptor function, including interactions with small molecules, protein partners, and DNA. We identify critical knowledge gaps that highlight the need for additional structural and mechanistic information regarding LuxI/R QS.