Genome-wide screens reveal Escherichia coli genes required for growth of T1-like phage LL5 and V5-like phage LL12.

The host factor requirements of phages and mechanisms of mutational phage insensitivity must be characterized for rational design of phage cocktails. To characterize host dependencies of two novel Escherichia coli phages, the T1-like siphophage LL5 and the V5-like myophage LL12, forward genetic screens were conducted against the Keio collection, a library of single non-essential gene deletions in E. coli str. BW25113. These screens and subsequent experiments identified genes required by phages LL5 and LL12. E. coli mutants deficient in heptose II and the phosphoryl substituent of heptose I of the inner core lipopolysaccharide (LPS) were unable to propagate phage LL5, as were mutants deficient in the outer membrane protein TolC. Mutants lacking glucose I of the LPS outer core failed to propagate LL12. Two additional genes encoding cytoplasmic chaperones, PpiB and SecB, were found to be required for efficient propagation of phage LL5, but not LL12. This screening approach may be useful for identifying host factors dependencies of phages, which would provide valuable information for their potential use as therapeutics and for phage engineering.

A family affair-Severe fetal and neonatal hemolytic anemia due to novel alpha-spectrin mutations in two siblings.

Hereditary spherocytosis (HS) is the most common cause of inherited, nonimmune hemolytic anemia. When inherited in an autosomal dominant fashion, the anemia is typically mild. However, severe, transfusion-dependent anemia is seen in autosomal recessive HS, which is often associated with deficient or absent red blood cell membrane protein alpha-spectrin. We report a 26-year-old para one who was referred to our center at 28 weeks' gestation due to concerns for fetal anemia. Evaluation revealed elevated peak systolic velocity in the middle cerebral artery by Doppler scan and fetal cardiomegaly. Fetal hematocrit obtained by sampling the umbilical vein was 9% confirming severe fetal anemia. Fetal peripheral smear was consistent with hereditary spherocytosis. Genetic analysis of both parents confirmed heterozygosity for the SPTA1 variants (pathogenic variant c.4180del (p.C1394Afs*25), and a variant of uncertain significance, c.1677G>T (p.G449G)) detected by a hemolytic anemia panel in the patient's first child. It is important to consider genetic causes of anemia in patients presenting with severe nonimmune fetal anemia, including autosomal recessive HS. We present a case of autosomal recessive HS with a novel pathogenic variant in the SPTA1 gene which resulted in significant impact on prenatal management.