angiostensyna
07.01.06, 11:03
Mam wielka prosbe-czy ktos umialby przetlumaczyc ponizszy tekst? nie moge
sobie z nim poradzic, niektorych slow w ogole nie ma w slowniku:/ bede
naprawde bardzo wdzieczna!
The formation of adhesive pili on the surface of Gram-negative
bacteria has been studied in detail, whereas
the pilus assembly pathways in Gram-positive bacteria
remain to be characterized. Gram-positive microbes use
the cell wall peptidoglycan as a surface organelle for
the covalent attachment of proteins; a strategy that
involves sorting signals of surface protein precursors
and sortase, a transpeptidase that cleaves sorting sig-nals
and links the C-terminus of surface proteins via an
amide bond to the peptidoglycan cross-bridge. Recent
studies with Actinomyces naeslundii, Corynebacterium
diphtheriae and Streptococcus parasanguis suggest
that some sortase enzymes catalyze protein polymeriz-ation
leading to the formation of pili on the surface of
Gram-positive bacteria. Arthobacter photogonimos and
Ruminococcus albus appear to use different strategies
for pilus assembly, consistent with the notion that
Gram-positive organisms, similar to Gram-negative
bacteria, have evolved multiple molecular strategies for
the formation of pili on microbial surfaces.
Attachment and colonization represent the initial stages of
bacterial infection [1]. Proteinaceous filaments on
microbial surfaces, known as pili or fimbriae, provide
adhesive functions during colonization and lead to the
establishment of respiratory, urinary, periodontal and
intestinal infectious diseases [2–5]. Analysis of the
structure and function of pili in Gram-negative bacteria
has revealed multiple intricate pathways that involve the
transport and assembly of proteins beyond the outer
membrane envelope and has also revealed pilus involve-ment
in bacterial motility [6,7]. An outer membrane
surface organelle does not exist in Gram-positive bacteria,
and because the molecular genetic analysis of these
microbes is less advanced, comparatively little is known
about pilus assembly in these organisms. The presence of
pili or fimbriae on the bacterial surface has been reported
for several strains of Corynebacterium spp., Actinomyces
spp. and Streptococcus spp. [8–11]. It has been proposed
that pili or fimbriae assembly in Gram-positive bacteria
might require unique factors, and one of these appears to
be the transpeptidase sortase surface proteins are anchored to the bacterial
cell wall.