Genome sequence and phenotypic characterization of Caulobacter segnis.

Caulobacter segnis is a unique species of Caulobacter that was initially deemed Mycoplana segnis because it was isolated from soil and appeared to share a number of features with other Mycoplana. After a 16S rDNA analysis showed that it was closely related to Caulobacter crescentus, it was reclassified C. segnis. Because the C. segnis genome sequence available in GenBank contained 126 pseudogenes, we compared the original sequencing data to the GenBank sequence and determined that many of the pseudogenes were due to sequence errors in the GenBank sequence. Consequently, we used multiple approaches to correct and reannotate the C. segnis genome sequence. In total, we deleted 247 bp, added 14 bp, and changed 8 bp resulting in 233 fewer bases in our corrected sequence. The corrected sequence contains only 15 pseudogenes compared to 126 in the original annotation. Furthermore, we found that unlike Mycoplana, C. segnis divides by fission, producing swarmer cells that have a single, polar flagellum.

Assessment of a Multifaceted Approach, Including Frequent PCR Testing, to Mitigation of COVID-19 Transmission at a Residential Historically Black University.

Importance: COVID-19 posed an unprecedented threat to residential colleges in the fall of 2020. While there were mathematical models of COVID-19 transmission, there were no established or tested protocols of COVID-19 testing or mitigation for school administrators to follow. Objective: To investigate the association of a multifaceted COVID-19 mitigation strategy using social, behavioral, and educational interventions and a program of frequent testing with prevalence of disease spread. Design, Setting, and Participants: This cohort study was conducted as a retrospective review of COVID-19 positivity from August 16, 2020, to April 30, 2021, at Delaware State University, a publicly funded historically Black university. Participants included all students, faculty, and staff members with a campus presence. Positivity rates after use of mitigation strategies and testing on campus were compared with those of the surrounding community. Data were analyzed from July through September 2021. Exposures: Mitigation strategies included education and outreach about social distancing, masking, and handwashing, and a COVID-19 testing plan consisted of twice-weekly polymerase chain reaction (PCR) screening using anterior nasal samples (fall and early spring semester) and then saliva-based samples (middle to late spring semester). Main Outcomes and Measures: Cumulative tests, infections, daily quarantine, and isolation residence hall occupancy were measured, and comparisons were made with statewide COVID-19 positivity rates. Results: The campus cohort included 2320 individuals (1575 resident students, 415 nonresident students, and 330 faculty or staff members). There were 1488 (64.1%) women and 832 (35.9%) men; mean (SD) age was 27.5 (12.9) years. During the fall semester, 36 500 COVID-19 PCR tests were performed. Weekly positivity rates ranged from 0 of 372 tests to 16 of 869 tests (1.8%) (mean [SD] positivity rate, 0.5% [0.5%]; 168 positive results and 36 312 negative results). During the same period, statewide positivity ranged from 589 of 25 120 tests (2.3%) to 5405 of 54 596 tests (9.9%) (mean [SD] positivity rate, 4.8% [2.6%]). In the spring semester, 39 045 PCR tests were performed. Weekly positivity rates ranged from 4 of 2028 tests (0.2%) to 36 of 900 tests (4.0%) (mean [SD] positivity rate, 0.8% [0.9%]; 267 positive results and 38 767 negative results). During the same period, statewide positivity ranged from 1336 of 37 254 tests (3.6%) to 3630 of 42 458 tests (8.5%) (mean [SD] positivity rate, 5.1% [1.3%]). Compared with statewide rates, campus positivity rates were mean (SD) 4.4 (2.6) percentage points lower during the fall semester (P < .001) and mean (SD) 5.6 (1.6) percentage points lower during the spring semester (P < .001). Total daily quarantine and isolation residence hall occupancy ranged from 0 to 43 students in the fall and 1 to 47 students during the spring. Conclusions and Relevance: This study found that the combination of campuswide mitigation policies and twice-weekly COVID-19 PCR screening was associated with a significant decrease in COVID-19 positivity at a residential historically Black university campus compared with the surrounding community. Given the socioeconomic demographics of many students at historically Black colleges and universities, keeping these resident campuses open is critical not only to ensure access to educational resources, but also to provide housing and food security.

Complete Genome Sequence of a Wild-Type Isolate of Caulobacter vibrioides Strain CB1.

The complete genome sequence of Caulobacter vibrioides strain CB1 consists of a chromosome of 4,137,285 bp, with a GC content of 67.2% and 3,990 coding DNA sequences. This strain contains the typical genome rearrangement that is characteristic of the Caulobacter strains that are currently sequenced. However, this strain is so closely related to sequenced strain NA1000 that rearrangements were minimal. This will allow further clarification of the causes of rearrangements in the species.

Complete Genome Sequence of a Wild-Type Isolate of Caulobacter vibrioides Strain CB2.

The complete genome of Caulobacter vibrioides strain CB2 consists of a 4,123,726-bp chromosome, a GC content of 67.2%, and 3,896 coding DNA sequences. It has no rearrangements but numerous indels relative to the reference NA1000 genome. This will allow us to study the impact of horizontal gene transfer on caulobacter genomes.