Stable kinetochore-microtubule attachment is sufficient to silence the spindle assembly checkpoint in human cells.

During mitosis, duplicated sister chromatids attach to microtubules emanating from opposing sides of the bipolar spindle through large protein complexes called kinetochores. In the absence of stable kinetochore-microtubule attachments, a cell surveillance mechanism known as the spindle assembly checkpoint (SAC) produces an inhibitory signal that prevents anaphase onset. Precisely how the inhibitory SAC signal is extinguished in response to microtubule attachment remains unresolved. To address this, we induced formation of hyper-stable kinetochore-microtubule attachments in human cells using a non-phosphorylatable version of the protein Hec1, a core component of the attachment machinery. We find that stable attachments are sufficient to silence the SAC in the absence of sister kinetochore bi-orientation and strikingly in the absence of detectable microtubule pulling forces or tension. Furthermore, we find that SAC satisfaction occurs despite the absence of large changes in intra-kinetochore distance, suggesting that substantial kinetochore stretching is not required for quenching the SAC signal.

Culture-based indicators of fecal contamination and molecular microbial indicators rarely correlate with Campylobacter spp. in recreational waters.

Campylobacter spp. are the leading cause of gastroenteritis worldwide. Most human infections result from contaminated food; however, infections are also caused by recreational waterway contamination. Campylobacter culture is technically challenging and enumeration by culture-based methods is onerous. Thus, we employed qPCR to quantify Campylobacter spp. in fresh- and marine-water samples, raw sewage and animal feces. Multiplex PCR determined whether Campylobacter jejuni or C. coli, most commonly associated with human disease, were present in qPCR-positive samples. Campylobacters were detected in raw sewage, and in feces of all avian and mammalian species tested. Campylobacter-positive concentrations ranged from 68 to 2.3 × 106 cells per 500 mL. Although C. jejuni and C. coli were rare in waterways, they were prevalent in sewage and feces. Campylobacter-specific qPCR screening of environmental waters did not correlate with the regulatory EPA method 1600 (Enterococcus culture), nor with culture-independent, molecular-based microbial source tracking indicators, such as human polyomavirus, human Bacteroidales and Methanobrevibacter smithii. Our results suggest that neither the standard EPA method nor the newly proposed culture-independent methods are appropriate surrogates for Campylobacter contamination in water. Thus, assays for specific pathogens may be necessary to protect human health, especially in waters that are contaminated with sewage and animal feces.