scholarly journals The Temporal Expression of Global Regulator Protein CsrA Is Dually Regulated by ClpP During the Biphasic Life Cycle of Legionella pneumophila

2019 ◽  
Vol 10 ◽  
Author(s):  
Zhen-huang Ge ◽  
Qin-sha Long ◽  
Pei-bo Yuan ◽  
Xin Pan ◽  
Dong Shen ◽  
...  
Keyword(s):  
Life Cycle ◽  
Legionella Pneumophila ◽  
Global Regulator ◽  
Temporal Expression ◽  
Regulator Protein ◽  
Biphasic Life Cycle

Stoichiometric implications of a biphasic life cycle

Oecologia ◽  
2015 ◽  
Vol 180 (3) ◽  
pp. 853-863 ◽  
Author(s):  
Scott D. Tiegs ◽  
Keith A. Berven ◽  
Douglas J. Carmack ◽  
Krista A. Capps
Keyword(s):  
Life Cycle ◽  
Biphasic Life Cycle

scholarly journals Studies on Bd0934 and Bd3507, Two Secreted Nucleases from Bdellovibrio bacteriovorus, Reveal Sequential Release of Nucleases during the Predatory Cycle

2020 ◽  
Vol 202 (18) ◽  
Author(s):  
Ewa Bukowska-Faniband ◽  
Tilde Andersson ◽  
Rolf Lood
Keyword(s):  
Antibiotic Resistance ◽  
Life Cycle ◽  
Antibiotic Resistance Genes ◽  
Human Pathogens ◽  
Temporal Expression ◽  
Bdellovibrio Bacteriovorus ◽  
Exogenous Dna ◽  
Content Type ◽  
Genes Encoding ◽  
Predatory Bacteria

ABSTRACT Bdellovibrio bacteriovorus is an obligate predatory bacterium that invades and kills a broad range of Gram-negative prey cells, including human pathogens. Its potential therapeutic application has been the subject of increased research interest in recent years. However, an improved understanding of the fundamental molecular aspects of the predatory life cycle is crucial for developing this bacterium as a “living antibiotic.” During intracellular growth, B. bacteriovorus secretes an arsenal of hydrolases, which digest the content of the host cell to provide growth nutrients for the predator, e.g., prey DNA is completely degraded by the nucleases. Here, we have, on a genetic and molecular level, characterized two secreted DNases from B. bacteriovorus, Bd0934 and Bd3507, and determined the temporal expression profile of other putative secreted nucleases. We conclude that Bd0934 and Bd3507 are likely a part of the predatosome but are not essential for the predation, host-independent growth, prey biofilm degradation, and self-biofilm formation. The detailed temporal expression analysis of genes encoding secreted nucleases revealed that these enzymes are produced in a sequential orchestrated manner. This work contributes to our understanding of the sequential breakdown of the prey nucleic acid by the nucleases secreted during the predatory life cycle of B. bacteriovorus. IMPORTANCE Antibiotic resistance is a major global concern with few available new means to combat it. From a therapeutic perspective, predatory bacteria constitute an interesting tool. They not only eliminate the pathogen but also reduce the overall pool of antibiotic resistance genes through secretion of nucleases and complete degradation of exogenous DNA. Molecular knowledge of how these secreted DNases act will give us further insight into how antibiotic resistance, and the spread thereof, can be limited through the action of predatory bacteria.

scholarly journals Haploid females in the isomorphic biphasic life-cycle of Gracilaria chilensis excel in survival

2018 ◽  
Vol 18 (1) ◽  
Author(s):  
Vasco M. N. C. S. Vieira ◽  
Aschwin H. Engelen ◽  
Oscar R. Huanel ◽  
Marie-Laure Guillemin
Keyword(s):  
Life Cycle ◽  
Gracilaria Chilensis ◽  
Biphasic Life Cycle

scholarly journals Genetic Evidence that Legionella pneumophila RpoS Modulates Expression of the Transmission Phenotype in Both the Exponential Phase and the Stationary Phase

2004 ◽  
Vol 72 (5) ◽  
pp. 2468-2476 ◽  
Author(s):  
Michael A. Bachman ◽  
Michele S. Swanson
Keyword(s):  
Life Cycle ◽  
Rna Polymerase ◽  
Stationary Phase ◽  
Growth Phase ◽  
Legionella Pneumophila ◽  
Opportunistic Pathogen ◽  
Sigma Factors ◽  
Exponential Phase ◽  
Posttranscriptional Control ◽  
Multiple Copies

ABSTRACT The opportunistic pathogen Legionella pneumophila alternates between two states: replication within phagocytes and transmission between host amoebae or macrophages. In broth cultures that model this life cycle, during the replication period, CsrA inhibits expression of transmission traits. When nutrients become limiting, the alarmone (p)ppGpp accumulates and the sigma factors RpoS and FliA and the positive activators LetA/S and LetE promote differentiation to the transmissible form. Here we show that when cells enter the postexponential growth phase, RpoS increases expression of the transmission genes fliA, flaA, and mip, factors L. pneumophila needs to establish a new replication niche. In contrast, in exponential (E)-phase cells whose (p)ppGpp levels are low, rpoS inhibits expression of transmission traits, on the basis of three separate observations. First, rpoS RNA levels peak in the E phase, suggestive of a role for RpoS during replication. Second, in multiple copies, rpoS decreases the amounts of csrA, letE, fliA, and flaA transcripts and inhibits the transmission traits of motility, infectivity, and cytotoxicity. Third, rpoS blocks expression of cytotoxicity and motility by E-phase bacteria that have been induced to express the LetA activator ectopically. The data are discussed in the context of a model in which the alarmone (p)ppGpp enables RpoS to outcompete other sigma factors for binding to RNA polymerase to promote transcription of transmission genes, while LetA/S acts in parallel to relieve CsrA posttranscriptional repression of the transmission regulon. By coupling transcriptional and posttranscriptional control pathways, intracellular L. pneumophila could respond to stress by rapidly differentiating to a transmissible form.

scholarly journals Integrating natural and sexual selection across the biphasic life cycle

2021 ◽  
Author(s):  
Craig Purchase ◽  
Jonathan Evans ◽  
Julissa Roncal
Keyword(s):  
Sexual Selection ◽  
Life Cycle ◽  
Natural Selection ◽  
Conceptual Framework ◽  
Life Cycles ◽  
Parental Effect ◽  
Biphasic Life Cycle ◽  
Evolutionary Trajectories ◽  
Taxonomic Groups ◽  
Natural And Sexual Selection

An alternation between diploid and haploid phases is universal among sexual eukaryotes. Across this biphasic cycle, natural selection and sexual selection occur in both phases. Together, these four stages of selection act on the phenotypes of individuals and influence the evolutionary trajectories of populations, but are rarely studied holistically. Here, we provide a conceptual framework that transcends taxonomic groups, and unifies the entire selection landscape within and across the diploid and haploid phases. Our synthesis produces six direct links among four selection stages, and from this we define four types of parental effect. We argue that knowledge of the complex and intertwined opportunities for selection within biphasic life cycles will offer clearer insights into key ecological and evolutionary processes, with benefits to applied science.

scholarly journals Rapid phenotypic evolution following shifts in life cycle complexity

2018 ◽  
Vol 285 (1871) ◽  
pp. 20172304 ◽  
Author(s):  
Ronald M. Bonett ◽  
John G. Phillips ◽  
Nicholus M. Ledbetter ◽  
Samuel D. Martin ◽  
Luke Lehman
Keyword(s):  
Life Cycle ◽  
Vertebral Column ◽  
Life Stages ◽  
Phenotypic Evolution ◽  
Trait Evolution ◽  
Life Cycle Stages ◽  
Biphasic Life Cycle ◽  
History Of ◽  
Life Cycle Evolution

Life cycle strategies have evolved extensively throughout the history of metazoans. The expression of disparate life stages within a single ontogeny can present conflicts to trait evolution, and therefore may have played a major role in shaping metazoan forms. However, few studies have examined the consequences of adding or subtracting life stages on patterns of trait evolution. By analysing trait evolution in a clade of closely related salamander lineages we show that shifts in the number of life cycle stages are associated with rapid phenotypic evolution. Specifically, salamanders with an aquatic-only (paedomorphic) life cycle have frequently added vertebrae to their trunk skeleton compared with closely related lineages with a complex aquatic-to-terrestrial (biphasic) life cycle. The rate of vertebral column evolution is also substantially lower in biphasic lineages, which may reflect the functional compromise of a complex cycle. This study demonstrates that the consequences of life cycle evolution can be detected at very fine scales of divergence. Rapid evolutionary responses can result from shifts in selective regimes following changes in life cycle complexity.

Brachiopoda

2017 ◽  
Author(s):  
Judith Fuchs ◽  
Andreas Altenburger
Keyword(s):  
Life Cycle ◽  
Tree Of Life ◽  
Filter Feeding ◽  
General Morphology ◽  
Biphasic Life Cycle ◽  
Family Level ◽  
Planktonic Larvae

This chapter describes the taxonomy of Brachiopoda, a phylum of exclusively marine, sessile, filter-feeding invertebrates. Brachiopods are meroplanktonik with a biphasic life cycle including planktonic larvae and sessile benthic adults. The chapter covers their life cycle, ecology, and general morphology. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.

scholarly journals A Unique cis -Encoded Small Noncoding RNA Is Regulating Legionella pneumophila Hfq Expression in a Life Cycle-Dependent Manner

mBio ◽  
2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Giulia Oliva ◽  
Tobias Sahr ◽  
Monica Rolando ◽  
Maike Knoth ◽  
Carmen Buchrieser
Keyword(s):  
Life Cycle ◽  
Virulence Factors ◽  
Legionella Pneumophila ◽  
Noncoding Rna ◽  
Acanthamoeba Castellanii ◽  
Severe Pneumonia ◽  
Dependent Manner ◽  
Rnase Iii ◽  
Small Noncoding Rna ◽  
Cycle Dependent

ABSTRACT Legionella pneumophila is an environmental bacterium that parasitizes protozoa, but it may also infect humans, thereby causing a severe pneumonia called Legionnaires’ disease. To cycle between the environment and a eukaryotic host, L. pneumophila is regulating the expression of virulence factors in a life cycle-dependent manner: replicating bacteria do not express virulence factors, whereas transmissive bacteria are highly motile and infective. Here we show that Hfq is an important regulator in this network. Hfq is highly expressed in transmissive bacteria but is expressed at very low levels in replicating bacteria. A L. pneumophila hfq deletion mutant exhibits reduced abilities to infect and multiply in Acanthamoeba castellanii at environmental temperatures. The life cycle-dependent regulation of Hfq expression depends on a unique cis -encoded small RNA named Anti-hfq that is transcribed antisense of the hfq transcript and overlaps its 5′ untranslated region. The Anti-hfq sRNA is highly expressed only in replicating L. pneumophila where it regulates hfq expression through binding to the complementary regions of the hfq transcripts. This results in reduced Hfq protein levels in exponentially growing cells. Both the small noncoding RNA (sRNA) and hfq mRNA are bound and stabilized by the Hfq protein, likely leading to the cleavage of the RNA duplex by the endoribonuclease RNase III. In contrast, after the switch to transmissive bacteria, the sRNA is not expressed, allowing now an efficient expression of the hfq gene and consequently Hfq. Our results place Hfq and its newly identified sRNA anti- hfq in the center of the regulatory network governing L. pneumophila differentiation from nonvirulent to virulent bacteria. IMPORTANCE The abilities of L. pneumophila to replicate intracellularly and to cause disease depend on its capacity to adapt to different extra- and intracellular environmental conditions. Therefore, a timely and fine-tuned expression of virulence factors and adaptation traits is crucial. Yet, the regulatory circuits governing the life cycle of L. pneumophila from replicating to virulent bacteria are only partly uncovered. Here we show that the life cycle-dependent regulation of the RNA chaperone Hfq relies on a small regulatory RNA encoded antisense to the hfq -encoding gene through a base pairing mechanism. Furthermore, Hfq regulates its own expression in an autoregulatory loop. The discovery of this RNA regulatory mechanism in L. pneumophila is an important step forward in the understanding of how the switch from inoffensive, replicating to highly virulent, transmissive L. pneumophila is regulated.

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