Draft Genome Sequences of Salmonella
enterica Serovar Typhimurium LT2 with
Deleted Chitinases That Are Emerging
Bihua C. Huang,
Bart C. Weimer
Department of Population Health and Reproduction, School of Veterinary Medicine, University of California,
Davis, California, USA
; 100K Pathogen Genome Project, University of California, Davis, California, USA
ABSTRACT Chitinases are glycosyl hydrolases that catalyze the hydrolysis of the
-1,4 linkages in complex carbohydrates and those that contain GlcNAc. These en-
zymes are considered emerging virulence factors during infection because the host
glycan changes. This is the release of four single chitinase deletion mutants in Sal-
monella enterica serovar Typhimurium LT2.
Chitinases are glycosyl hydrolases (GHs) that belong to the GH18 and GH19 families
(1–6). GH enzymes play a signiﬁcant role in virulence by altering the host glycan
structure during infection and gaining access to the host epithelial cells, which results
in the microbe binding to terminal monosaccharides to initiate glycan degradation on
the host epithelial cell (7, 8). Chitinases are emerging virulence factors because they
recognize host GlcNAc-containing glycans in mucin and other N-glycosylated proteins
in the host membrane, which enable host association as well as glycan digestion, to
gain access to the cell membrane to initiate invasion (9, 10). Glycans with GlcNAc
molecules with a
-1,4-glycosidic bond (11) are found on intestinal epithelial cells (IECs)
and are hydrolyzed during association (1, 10). This provides Salmonella spp. a method
to degrade the glycan and digest the glycocalyx to establish intracellular infections.
Deletion of chitinase genes in Listeria monocytogenes led to a reduction in bacterial
counts in the liver and spleen of infected mice (12). An adherent-invasive Escherichia
coli (AIEC) LF82 deletion of the chiA gene signiﬁcantly reduced the adhesion to IECs
compared to that of the wild type (13). Furthermore, AIEC LF82 interacted with an
N-glycosylated chitin-binding protein (CHI3L1) on the host cell to mediate close
interaction between the host membrane and bacterial cell, which is regulated in animal
models of colitis and in human inﬂammatory bowel diseases (IBDs) (14). Microarray
analysis showed that SL0018 (chiA) gene in the Salmonella SL1344 strain was strongly
induced during the infection of murine macrophage cells (15, 16). These data indicate
that chitinases relandscape the host glycan to promote the attachment of bacteria to
the host cells through the interaction with mucin or N-glycosylated glycans during
association. The genus Salmonella contains four chitinases that were derived from
bacteria and phages. Park et al. (8) also demonstrated that Salmonella initiates glycan
relandscaping during infection via host gene expression changes and microbe grazing
to degrade the glycan, making these enzymes important for infection.
The 100K Pathogen Genome Project (http://www.100kgenomes.org) is a large-scale
sequencing consortium that offers the use of new next-generation sequencing meth-
ods to provide cutting-edge methods for pathogen detection and control in the food
supply. This project is focused on sequencing genomes of bacteria from the environ-
ment, plants, animals, and humans worldwide, providing new insights into the genetic
diversity of pathogens and the microbiome. Four chitinase deletions (⌬STM0018,
Received 23 May 2017 Accepted 25 May
2017 Published 3 August 2017
Citation Arabyan N, Huang BC, Weimer BC.
2017. Draft genome sequences of Salmonella
enterica serovar Typhimurium LT2 with deleted
chitinases that are emerging virulence factors.
Genome Announc 5:e00659-17. https://doi
Copyright © 2017 Arabyan et al. This is an
open-access article distributed under the terms
of the Creative Commons Attribution 4.0
Address correspondence to Bart C. Weimer,
Volume 5 Issue 31 e00659-17 genomea.asm.org 1
⌬STM0233,⌬STM0907, and ⌬STM1869A) were constructed in the Weimer laboratory
(University of California, Davis) (7) as described by Datsenko and Wanner (17). Cultures
were prepared for sequencing as described previously (18–25). Genome sequences
were de novo assembled using CLC Workbench version 6.5.1 with default parameters
Accession number(s). All sequences are publicly available and can be found at the
100K Pathogen Genome Project BioProject (NCBI PRJNA186441) in the Sequence Read
Archive (http://www.ncbi.nlm.nih.gov/sra). NCBI GenBank accession numbers for the
genome assemblies are listed in Table 1.
B.C.W. is grateful for the funding contributed by the NIH (1R01HD065122-01A1;
NIH-U24-DK097154) and an Agilent Technologies Thought Leader Award.
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TABLE 1 Salmonella enterica serovar Typhimurium LT2 chitinase deletion mutants
deleted Enzyme activity
No. of coding
MZNQ00000000 SRR5288763 BCW_8404 ⌬STM0018 Exochitinase 61 139 4,893,048 4,810
MXBA00000000 SRR5288762 BCW_8406 ⌬STM0233 Endochitinase 63 162 4,894,557 4,808
MXBB00000000 SRR5288761 BCW_8409 ⌬STM0907 Prophage chitinase 61 188 4,895,634 4,808
MZYL00000000 SRR5288732 BCW_8417 ⌬STM1869A Putative chitinase 63 177 4,895,461 4,811
Arabyan et al.
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