scholarly journals Unraveling the mechanism of action of a new type III secretion system effector AexU from Aeromonas hydrophila

2010 ◽  
Vol 49 (3) ◽  
pp. 122-134 ◽  
Author(s):  
Johanna C. Sierra ◽  
Giovanni Suarez ◽  
Jian Sha ◽  
Wallace B. Baze ◽  
Sheri M. Foltz ◽  
...  
Keyword(s):  
Mechanism Of Action ◽  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii ◽  
New Type

Biological characterization of a new type III secretion system effector from a clinical isolate of Aeromonas hydrophila—Part II

2007 ◽  
Vol 43 (4) ◽  
pp. 147-160 ◽  
Author(s):  
Johanna C. Sierra ◽  
Giovanni Suarez ◽  
Jian Sha ◽  
Sheri M. Foltz ◽  
Vsevolod L. Popov ◽  
...  
Keyword(s):  
Clinical Isolate ◽  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Biological Characterization ◽  
Type Iii ◽  
New Type

scholarly journals The Type III Secretion System and Cytotoxic Enterotoxin Alter the Virulence of Aeromonas hydrophila

2005 ◽  
Vol 73 (10) ◽  
pp. 6446-6457 ◽  
Author(s):  
Jian Sha ◽  
Lakshmi Pillai ◽  
Amin A. Fadl ◽  
Cristi L. Galindo ◽  
Tatiana E. Erova ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Cultured Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gene Encoding ◽  
Type Iii ◽  
Isogenic Mutants

ABSTRACT Many gram-negative bacteria use a type III secretion system (TTSS) to deliver effector proteins into host cells. Here we report the characterization of a TTSS chromosomal operon from the diarrheal isolate SSU of Aeromonas hydrophila. We deleted the gene encoding Aeromonas outer membrane protein B (AopB), which is predicted to be involved in the formation of the TTSS translocon, from wild-type (WT) A. hydrophila as well as from a previously characterized cytotoxic enterotoxin gene (act)-minus strain of A. hydrophila, thus generating aopB and act/aopB isogenic mutants. The act gene encodes a type II-secreted cytotoxic enterotoxin (Act) that has hemolytic, cytotoxic, and enterotoxic activities and induces lethality in a mouse model. These isogenic mutants (aopB, act, and act/aopB) were highly attenuated in their ability to induce cytotoxicity in RAW 264.7 murine macrophages and HT-29 human colonic epithelial cells. The act/aopB mutant demonstrated the greatest reduction in cytotoxicity to cultured cells after 4 h of infection, as measured by the release of lactate dehydrogenase enzyme, and was avirulent in mice, with a 90% survival rate compared to that of animals infected with Act and AopB mutants, which caused 50 to 60% of the animals to die at a dose of three 50% lethal doses. In contrast, WT A. hydrophila killed 100% of the mice within 48 h. The effects of these mutations on cytotoxicity could be complemented with the native genes. Our studies further revealed that the production of lactones, which are involved in quorum sensing (QS), was decreased in the act (32%) and aopB (64%) mutants and was minimal (only 8%) in the act/aopB mutant, compared to that of WT A. hydrophila SSU. The effects of act and aopB gene deletions on lactone production could also be complemented with the native genes, indicating specific effects of Act and the TTSS on lactone production. Although recent studies with other bacteria have indicated TTSS regulation by QS, this is the first report describing a correlation between the TTSS and Act of A. hydrophila and the production of lactones.

scholarly journals A Type III Secretion System Is Required for Aeromonas hydrophila AH-1 Pathogenesis

2004 ◽  
Vol 72 (3) ◽  
pp. 1248-1256 ◽  
Author(s):  
H. B. Yu ◽  
P. S. Srinivasa Rao ◽  
H. C. Lee ◽  
S. Vilches ◽  
S. Merino ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Gene Clusters ◽  
Opportunistic Pathogen ◽  
Secretion System ◽  
Virulence Determinants ◽  
Degenerate Primers ◽  
Type Iii ◽  
Insertional Inactivation

ABSTRACT Aeromonas hydrophila is a gram-negative opportunistic pathogen in fish and humans. Many bacterial pathogens of animals and plants have been shown to inject anti-host virulence determinants into the hosts via a type III secretion system (TTSS). Degenerate primers based on lcrD family genes that are present in every known TTSS allowed us to locate the TTSS gene cluster in A. hydrophila AH-1. A series of genome walking steps helped in the identification of 25 open reading frames that encode proteins homologous to those in TTSSs in other bacteria. PCR-based analysis showed the presence of lcrD homologs (ascV) in all of the 33 strains of A. hydrophila isolated from various sources. Insertional inactivation of two of the TTSS genes (aopB and aopD) led to decreased cytotoxicity in carp epithelial cells, increased phagocytosis, and reduced virulence in blue gourami. These results show that a TTSS is required for A. hydrophila pathogenesis. This is the first report of sequencing and characterization of TTSS gene clusters from A. hydrophila. The TTSS identified here may help in developing suitable vaccines as well as in further understanding of the pathogenesis of A. hydrophila.

Deletion of the genes encoding the type III secretion system and cytotoxic enterotoxin alters host responses to Aeromonas hydrophila infection

2006 ◽  
Vol 40 (5) ◽  
pp. 198-210 ◽  
Author(s):  
Amin A. Fadl ◽  
Cristi L. Galindo ◽  
Jian Sha ◽  
Tatiana E. Erova ◽  
Clifford W. Houston ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Responses ◽  
Type Iii ◽  
Genes Encoding

scholarly journals Aeromonas hydrophila AH-3 Type III Secretion System Expression and Regulatory Network

2009 ◽  
Vol 75 (19) ◽  
pp. 6382-6392 ◽  
Author(s):  
Silvia Vilches ◽  
Natalia Jimenez ◽  
Juan M. Tomás ◽  
Susana Merino
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Regulatory Network ◽  
Type Iii Secretion System ◽  
High Growth ◽  
Secretion System ◽  
Magnesium Concentration ◽  
Two Component System ◽  
Calcium Depletion ◽  
Type Iii

ABSTRACT The Aeromonas hydrophila type III secretion system (T3SS) has been shown to play a crucial role in this pathogen's interactions with its host. We previously described the genetic organization of the T3SS cluster and the existence of at least one effector, called AexT, in A. hydrophila strain AH-3. In this study, we analyzed the expression of the T3SS regulon by analyzing the activity of the aopN-aopD and aexT promoters (T3SS machinery components and effector, respectively) by means of two different techniques: promoterless gfp fusions and real-time PCR. The expression of the A. hydrophila AH-3 T3SS regulon was induced in response to several environmental factors, of which calcium depletion, a high magnesium concentration, and a high growth temperature were shown to be the major ones. Once the optimal conditions were established, we tested the expression of the T3SS regulon in the background of several virulence determinant knockouts of strain AH-3. The analysis of the data obtained from axsA and aopN mutants, both of which have been described to be T3SS regulators in other species, allowed us to corroborate their function as the major transcription regulator and valve of the T3SS, respectively, in Aeromonas hydrophila. We also demonstrated the existence of a complicated interconnection between the expression of the T3SS and several other different virulence factors, such as the lipopolysaccharide, the PhoPQ two-component system, the ahyIR quorum sensing system, and the enzymatic complex pyruvate deshydrogenase. To our knowledge, this is the first study of the A. hydrophila T3SS regulatory network.

Aeromonas hydrophila AH-3 AexT is an ADP-ribosylating toxin secreted through the type III secretion system

2008 ◽  
Vol 44 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Silvia Vilches ◽  
Markus Wilhelms ◽  
Hong Bing Yu ◽  
Ka Yin Leung ◽  
Juan M. Tomás ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii

Detection of type III secretion system genes in Aeromonas hydrophila and their relationship with virulence in Nile tilapia

2010 ◽  
Vol 144 (3-4) ◽  
pp. 371-376 ◽  
Author(s):  
G.A. Carvalho-Castro ◽  
C.O. Lopes ◽  
C.A.G. Leal ◽  
P.G. Cardoso ◽  
R.C. Leite ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Nile Tilapia ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii
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