scholarly journals The secret life (cycle) of temperate bacteriophages

2021 ◽  
Author(s):  
Alfred Fillol-Salom ◽  
Rodrigo Bacigalupe ◽  
Suzanne Humphrey ◽  
Yin Ning Chiang ◽  
John Chen ◽  
...  
Keyword(s):  
Life Cycle ◽  
Gene Transfer ◽  
Lytic Cycle ◽  
Genetic Analyses ◽  
Phage P22 ◽  
Phage Production ◽  
Stable Association ◽  
Temporal Program

AbstractLysogenic induction ends the stable association between a bacteriophage and its host, and the transition to the lytic cycle begins with prophage excision followed by DNA replication and packaging (ERP) – a temporal program that is considered universal for most temperate phages. Here we report that the long-standing ERP program is an artefact of the experimentally favoured Salmonella phage P22 tsc229 heat-inducible mutant, and that wildtype P22 actually follows a replication-packaging-excision (RPE) program. We found that unlike P22 tsc229, P22 delayed excision to just before it was detrimental to phage production. Thus, at minimal expense to itself, P22 has tuned the timing of excision to balance propagation with lateral transduction, powering the evolution of its host through gene transfer in the interest of self-preservation.One Sentence SummaryGenetic analyses propose a new life cycle for temperate bacteriophages.

scholarly journals Lateral transduction is inherent to the life cycle of the archetypical Salmonella phage P22

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alfred Fillol-Salom ◽  
Rodrigo Bacigalupe ◽  
Suzanne Humphrey ◽  
Yin Ning Chiang ◽  
John Chen ◽  
...  
Keyword(s):  
Life Cycle ◽  
Gene Transfer ◽  
Direct Evidence ◽  
Lytic Cycle ◽  
Wild Type ◽  
Phage P22 ◽  
Phage Production ◽  
Stable Association ◽  
Salmonella Phage ◽  
Temporal Program

AbstractLysogenic induction ends the stable association between a bacteriophage and its host, and the transition to the lytic cycle begins with early prophage excision followed by DNA replication and packaging (ERP). This temporal program is considered universal for P22-like temperate phages, though there is no direct evidence to support the timing and sequence of these events. Here we report that the long-standing ERP program is an observation of the experimentally favored Salmonella phage P22 tsc229 heat-inducible mutant, and that wild-type P22 actually follows the replication-packaging-excision (RPE) program. We find that P22 tsc229 excises early after induction, but P22 delays excision to just before it is detrimental to phage production. This allows P22 to engage in lateral transduction. Thus, at minimal expense to itself, P22 has tuned the timing of excision to balance propagation with lateral transduction, powering the evolution of its host through gene transfer in the interest of self-preservation.

scholarly journals Microtubule depolymerization activates the Epstein–Barr virus lytic cycle through protein kinase C pathways in nasopharyngeal carcinoma cells

2013 ◽  
Vol 94 (12) ◽  
pp. 2750-2758 ◽  
Author(s):  
Yi-Ru Liu ◽  
Sheng-Yen Huang ◽  
Jen-Yang Chen ◽  
Lily Hui-Ching Wang
Keyword(s):  
Protein Kinase C ◽  
Life Cycle ◽  
Protein Kinase ◽  
Nasopharyngeal Carcinoma ◽  
Epstein Barr Virus ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Kinase C ◽  
Epstein Barr ◽  
In Cells

Elevated levels of antibodies against Epstein–Barr virus (EBV) and the presence of viral DNA in plasma are reliable biomarkers for the diagnosis of nasopharyngeal carcinoma (NPC) in high-prevalence areas, such as South-East Asia. The presence of these viral markers in the circulation suggests that a minimal level of virus reactivation may have occurred in an infected individual, although the underlying mechanism of reactivation remains to be elucidated. Here, we showed that treatment with nocodazole, which provokes the depolymerization of microtubules, induces the expression of two EBV lytic cycle proteins, Zta and EA-D, in EBV-positive NPC cells. This effect was independent of mitotic arrest, as viral reactivation was not abolished in cells synchronized at interphase. Notably, the induction of Zta by nocodazole was mediated by transcriptional upregulation via protein kinase C (PKC). Pre-treatment with inhibitors for PKC or its downstream signalling partners p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) abolished the nocodazole-mediated induction of Zta and EA-D. Interestingly, the effect of nocodazole, as well as colchicine and vinblastine, on lytic gene expression occurred only in NPC epithelial cells but not in cells derived from lymphocytes. These results establish a novel role of microtubule integrity in controlling the EBV life cycle through PKC and its downstream pathways, which represents a tissue-specific mechanism for controlling the life-cycle switch of EBV.

scholarly journals THE GENETIC SYSTEM CONTROLLING HOMOTHALLISM IN SACCHAROMYCES YEASTS

Genetics ◽  
1974 ◽  
Vol 77 (4) ◽  
pp. 639-650
Author(s):  
Satoshi Harashima ◽  
Yasuhisa Nogi ◽  
Yasuji Oshima
Keyword(s):  
Life Cycle ◽  
Mating Type ◽  
Genetic System ◽  
Life Cycles ◽  
Single Pair ◽  
Type I ◽  
Type Ii ◽  
Genetic Analyses ◽  
Type Locus ◽  
Controlling Elements

ABSTRACT There are four types of life cycles in Saccharomyces cerevisiae and its related species. A perfect homothallic life cycle (the Ho type) is observed in the classic D strain. Two other types show semi-homothallism; one of them shows a 2-homothallic diploid:2α heterothallic haploid segregation (the Hp type) and another, a 2-homothallic:2a segregation (the Hq type). In the segregants from these Ho, Hp, and Hq diploids, each homothallic segregant shows the same segregation pattern as its parental diploid. The fourth type has a heterothallic life cycle showing a 2a:2α segregation and the diploids are produced by the fusion of two haploid cells of opposite mating types. The diploids prepared by the crosses of α Hp (an α haploid segregant from the Hp diploid) to a Hq (an a haploid from the Hq diploid) segregated two types (Type I and II) of the Ho type homothallic clone among their meiotic segregants. Genetic analyses were performed to investigate this phenomenon and the genotypes of the Ho type homothallic clones of Type I and Type II. Results of these genetic analyses have been most adequately explained by postulating three kinds of homothallic genes, each consisting of a single pair of alleles, HO/ho, HMα/hmα, and HMa/hma, respectively. One of them, the HMα locus, was proved to be loosely linked (64 stranes) to the mating-type locus. A spore having the HO hmα hma genotype gives rise to an Ho type homothallic diploid (Type I), the same as in the case of the D strain which has the HO HMα HMa genotype (Type II). A spore having the a HO hmα HMa or α HO HMα hma genotype will produce an Hp or Hq type homothallic diploid culture, respectively. The other genotypes, a HO HMα hma, α HO hmα HMa, and the genotypes combined with the ho allele give a heterothallic character to the spore culture. A possible molecular hypothesis for the mating-type differentiation with the controlling elements produced by the HMα and HMa genes is proposed.

scholarly journals Hybrid Breakdown in the F1 between Solanum chacoense and S. phureja and Gene Transfer for Leptine Biosynthesis

1998 ◽  
Vol 123 (5) ◽  
pp. 854-858 ◽  
Author(s):  
Richard E. Veilleux ◽  
A. Raymond Miller
Keyword(s):  
Life Cycle ◽  
Gene Transfer ◽  
Anther Culture ◽  
Solanum Chacoense ◽  
Hybrid Breakdown ◽  
Backcross Hybrids ◽  
Backcross Populations

F1 hybrids between high leptine-producing clones (8380-1, PI 458310 and 55-1) of Solanum chacoense Bitt. and anther culture competent or anther-derived clones of S. phureja Juz. & Buk. that did not produce leptines were generally weak plants that grew slowly and died before flowering. Exceptional hybrids could be found that were capable of completing a life cycle, especially during the hot summer months in the greenhouse. All F1 hybrids produced leptines in the leaves but not the tubers, albeit at lower levels than in the S. chacoense parent. Anther-derived monoploids from the F1 hybrids exhibited a range of leptine production from none to levels approaching the S. chacoense parent. Backcross populations of an F1 hybrid to the S. chacoense and S. phureja parents were examined for leptine production. Backcross hybrids were generally much more vigorous than the F1 hybrids. All of the S. chacoense backcrosses produced leptines ranging from intermediate to high levels; four of the twelve S. phureja backcrosses exhibited low leptine levels. A general dominance of leptine synthesis was therefore exhibited, although the nonleptine-producing parent affected the expression of leptines in the hybrids.

scholarly journals The life-cycle of Toxoplasma gondii reviewed using animations

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Márcia Attias ◽  
Dirceu E. Teixeira ◽  
Marlene Benchimol ◽  
Rossiane C. Vommaro ◽  
Paulo Henrique Crepaldi ◽  
...  
Keyword(s):  
Life Cycle ◽  
Toxoplasma Gondii ◽  
Cell Model ◽  
Protozoan Parasite ◽  
Lytic Cycle ◽  
High Prevalence ◽  
Unique Cell ◽  
Transmission Pathways ◽  
And Control ◽  
Important Parasite

AbstractToxoplasma gondii is a protozoan parasite that is the causative agent of toxoplasmosis, an infection with high prevalence worldwide. Most of the infected individuals are either asymptomatic or have mild symptoms, but T. gondii can cause severe neurologic damage and even death of the fetus when acquired during pregnancy. It is also a serious condition in immunodeficient patients. The life-cycle of T. gondii is complex, with more than one infective form and several transmission pathways. In two animated videos, we describe the main aspects of this cycle, raising questions about poorly or unknown issues of T. gondii biology. Original plates, based on electron microscope observations, are also available for teachers, students and researchers. The main goal of this review is to provide a source of learning on the fundamental aspects of T. gondii biology to students and teachers contributing for better knowledge and control on this important parasite, and unique cell model. In addition, drawings and videos point to still unclear aspects of T. gondii lytic cycle that may stimulate further studies.

scholarly journals Acyl-Homoserine Lactones Can Induce Virus Production in Lysogenic Bacteria: an Alternative Paradigm for Prophage Induction

2009 ◽  
Vol 75 (22) ◽  
pp. 7142-7152 ◽  
Author(s):  
Dhritiman Ghosh ◽  
Krishnakali Roy ◽  
Kurt E. Williamson ◽  
Sharath Srinivasiah ◽  
K. Eric Wommack ◽  
...  
Keyword(s):  
Virus Production ◽  
Lytic Cycle ◽  
Prophage Induction ◽  
Homoserine Lactones ◽  
E Coli ◽  
Acyl Homoserine Lactones ◽  
Induction Process ◽  
Phage Production ◽  
Viral Reproduction

ABSTRACT Prophage typically are induced to a lytic cycle under stressful environmental conditions or when the host's survival is threatened. However, stress-independent, spontaneous induction also occurs in nature and may be cell density dependent, but the in vivo signal(s) that can trigger induction is unknown. In the present study, we report that acyl-homoserine lactones (AHL), the essential signaling molecules of quorum sensing in many gram-negative bacteria, can trigger phage production in soil and groundwater bacteria. This phenomenon also was operative in a λ lysogen of Escherichia coli. In model coculture systems, we monitored the real-time AHL production from Pseudomonas aeruginosa PAO1 using an AHL bioluminescent sensor and demonstrated that λ-prophage induction in E. coli was correlated with AHL production. As a working model in E. coli, we show that the induction responses of λ with AHL remained unaffected when recA was deleted, suggesting that this mechanism does not involve an SOS response. In the same λ lysogen we also demonstrated that sdiA, the AHL receptor, and rcsA, a positive transcriptional regulator of exopolysaccharide synthesis, are involved in the AHL-mediated induction process. These findings relate viral reproduction to chemical signals associated with high host cell abundance, suggesting an alternative paradigm for prophage induction.

scholarly journals SPECIALIZED TRANSDUCING PHAGES DERIVED FROM PHAGE P22 THAT CARRY THE proAB REGION OF THE HOST, SALMONELLA TYPHIMURIUM: GENETIC EVIDENCE FOR THEIR STRUCTURE AND MODE OF TRANSDUCTION

Genetics ◽  
1976 ◽  
Vol 83 (3) ◽  
pp. 459-475
Author(s):  
Adrienne P Jessop
Keyword(s):  
Salmonella Typhimurium ◽  
Mixed Infection ◽  
Genetic Evidence ◽  
Lytic Cycle ◽  
Single Infection ◽  
Wild Type ◽  
Bacterial Dna ◽  
Phage P22

ABSTRACT Two independently isolated specialized transducing phages, P22pro-1 and P22pro-3, have been studied. Lysates of P22pro-1contain a majority of transducing phages which can go through the lytic cycle only in mixed infection; these defective phages transduce by lysogenization in mixed infection and by substitution in single infection. A few of the transducing phages in P22pro-1 lysates appear to be non-defective, being able to form plaques and to transduce by lysogenization in single infection. Transduction by P22pro-3 lysates is effected by non-defective transducing phages, which transduce by lysogenization; these lysates also contain a majority of defective phages which do not co-operate in mixed infection. The P22pro-1 genome is thought to contain an insertion of bacterial DNA longer than the terminal repetition present in P22 wild type, so that at maturation a population of differently defective phages is produced. The exact structure of the P22pro-3 genome is open to conjecture, but it seems clear that the insertion of bacterial DNA is smaller than that in P22pro-1. Both P22pro-1 and P22pro-3 are defective in integration at ataA under non-selective conditions, although both integrate on medium that lacks proline.

scholarly journals GENETICS OF THE ST SEROTYPE SYSTEM IN TETRAHYMENA PYRIFORMIS, SYNGEN 1

Genetics ◽  
1972 ◽  
Vol 70 (4) ◽  
pp. 521-536
Author(s):  
Frank S Grass
Keyword(s):  
Life Cycle ◽  
Mating Type ◽  
Genetic Locus ◽  
Tetrahymena Pyriformis ◽  
The Other ◽  
Genetic Analyses ◽  
Output Ratio

ABSTRACT Genetic analyses using lines of Tetrahymena pyroformis manifesting different serotypes indicate that the St serotypes are governed by alleles at a single genetic locus. These alleles are termed StA and StC. The St locus is not closely linked to any of the other well-studied loci examined. Differentiation in StA/StC heterozygotes follows a pattern very similar to that observed with lines heterozygous at the other loci. Initially both alleles are expressed, but as the synclone divides, lines develop that manifest one allele or the other but not both. The time of differentiation is very early in the clonal life cycle, and the output ratio is eccentric. The pattern of development of the St locus places it in a category with the mating type and H serotype loci.

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