This work investigated degradation (measured by qPCR) and biological deactivation (measured by culturebased natural transformation) of extra-and intracellular antibiotic resistance genes (eARGs and iARGs) by free available chlorine (FAC), NH 2 Cl, O 3 , ClO 2 , and UV light (254 nm), and of eARGs by • OH, using a chromosomal ARG (blt) of multidrug-resistant Bacillus subtilis 1A189. Rate constants for degradation of four 266−1017 bp amplicons adjacent to or encompassing the acfA mutation enabling blt overexpression increased in proportion to #AT+GC bps/ amplicon, or in proportion to #5′-GG-3′ or 5′-TT-3′ doublets/amplicon, with respective values ranging from 0.59 to 2.3 (×10 11 M −1 s −1 ) for • OH, 1.8−6.9 (×10 4 M −1 s −1 ) for O 3 , 3.9−9.2 (×10 3 M −1 s −1 ) for FAC, 0.35−1.2(×10 1 M −1 s −1 ) for ClO 2 , and 2.0−8.8 (×10 −2 cm 2 /mJ) for UV at pH 7, and from 1.7−4.4 M −1 s −1 for NH 2 Cl at pH 8. For FAC, NH 2 Cl, O 3 , ClO 2 , and UV, ARG deactivation paralleled degradation of amplicons approximating a ∼800−1000 bp acfA-flanking sequence required for natural transformation in B. subtilis, whereas deactivation outpaced degradation for • OH. At practical disinfectant exposures, eARGs and iARGs were ≥90% degraded/deactivated by FAC, O 3 , and UV, but recalcitrant to NH 2 Cl and ClO 2 . iARG degradation/deactivation always lagged cell inactivation. These findings provide a quantitative framework for evaluating ARG fate during disinfection/oxidation, and support using qPCR as a proxy for tracking ARG deactivation under carefully selected circumstances.

Streptococcus suis serotype 2 (S. suis 2) has evolved into a highly invasive pathogen that was found to be the cause of 2 large-scale outbreaks of streptococcus toxic shock syndrome (STSS) in China. However, the mechanism of action of this non-group A streptococcal (GAS) S. suis-caused STSS is still unknown. Previously, we identified a unique pathogenicity island (PAI) designated 89K that is specific to the STSS-causing epidemic strains of S. suis 2. In this study, we further report a functional type IV-like secretion system (T4SS-like system) harbored in the 89K PAI that contributes to the development of STSS. Knockout of the 2 key components (VirD4-89K and VirB4-89K) of the T4SS-like system eliminated the lethality of the highly virulent strain and impaired its ability to trigger host immune response in experimental infection of mice. Our findings provide a new insight into the pathogenesis of STSS caused by the highly pathogenic S. suis 2 isolates.

Fusarium wilt of banana (FWB) is the main threatening factor for banana production worldwide. To explore bacterial biocontrol resources for FWB, the antagonistic effective strains were isolated from banana-producing areas in Yunnan Province, China. Two isolates (YN0904 and YN1419) displaying strong antagonism against Tropical Race 4 (TR4) were identified from a total of 813 strains of endophytic bacteria. TR4 inhibition rates of YN0904 and YN1419 were 79.6% and 81.3%, respectively. By looking at morphological, molecular, physiological and biochemical characteristics, YN0904 was identified as Bacillus amyloliquefaciens, while YN1419 was identified as as B. subtillis. The control effects of YN0904 and YN1419 on TR4 in greenhouse experiments were 82.6% and 85.6%, respectively. Furthermore, YN0904 obviously promoted the growth of banana plantlets. In addition, biocontrol marker genes related to the biosynthesis of antibiotics synthesized and auxin key synthetase genes could be detected in YN0904. Surprisingly, the marker gene sboA could be exclusively detected in YN1419, while other marker genes were all absent. Molecular characterization results could provide a theoretical basis for expounding the biocontrol mechanisms of these two strains. We concluded that natively antagonistic strains derived from local banana plantations could provide new biological control resources for FWB.

No abstract

No abstract