Biology Reference
In-Depth Information
An FHb (GenBank Accession No. FJ874761) has been briefly reported
to be expressed in
Cylindrocarpon
(
Kim, Fushinobu, Zhou, Wakagi, &
Shoun, 2010
), a common soil-borne fungus, which causes root rot in many
plant species, but this sequence was not found in our analyses.
6.4. Protozoa
The anti-parasitic effects of nitric oxide have been widely documented in
Protozoa and Metazoa (reviewed in
Ascenzi, Bocedi, & Gradoni, 2003
);
however, the defence mechanisms against NO and RNS that must be asso-
ciated with efficient invasion and colonization of the host by pathogens are
incompletely understood. In pathogenic bacteria, the presence of
haemoglobins (e.g. FHb in
E. coli
and
Salmonella
, a TrHb in
Mycobacterium
tuberculosis
and an SDgb in
Campylobacter jejuni
; for a review see
Bowman
et al., 2011
) represents the main mechanisms involved in resistance to
nitrosative stress (
Bowman et al., 2011; Vinogradov et al., 2013
). On the
other hand, a number of pathogenic protozoal genomes lack globin-like
sequences (Supplementary Table S1 at
http://www.elsevierdirect.com/
companions/9780124076938
)
. For instance, production by iNOS of NO
from
L
-arginine by human macrophages is involved in
Leishmania
killing
(
Green, Meltzer, Hibbs, & Nacy, 1990; Liew, Millott, Parkinson,
Palmer, & Moncada, 1990
). However, evasion and survival strategies of
the protozoan include the suppression of the iNOS induction and the entry
into iNOS-negative target cells (
Bogdan, Gessner, Solbach, & Rollinghoff,
1996
). Clinical manifestations of American tegumentary leishmaniasis
(ATL) in the New World are mainly associated with
Leishmania
(
Viannia
)
braziliensis
and
Leishmania
(
Leishmania
)
mexicana
and NO-resistant isolates
of these parasites have been reported and related to disease severity
(
Giudice et al., 2007
). The lack of globin-like sequences in the
L
.
braziliensis
genome indicates a different, unidentified mechanism(s) to detoxify NO but
L. mexicana
does have sequences encoding two globin-like sensors; whether
these gene products are related to NO detoxification is unknown.
Activated macrophages kill
Entamoeba histolytica
trophozoites (Supple-
mentary Table S1 at
http://www.elsevierdirect.com/companions/
9780124076938
)
mainly by NO production (
Denis & Chadee, 1989;
Lin, Seguin, Keller, & Chadee, 1994
). The presence of NO severely
compromises the viability of this parasite by triggering an apoptosis-like
mechanism (
Ramos et al., 2007
) producing profound morphological
modifications such as generation of vesicle-like structures of the atypical