Type II fatty acid biosynthesis in bacteria can be broadly classified into the initiation and elongation phases. The biochemical functions defining each step in the two phases have been studied in vitro. Among the β-ketoacyl-acyl carrier protein (ACP) synthases, FabH catalyzes the initiation reaction, while FabB and FabF, which primarily catalyze the elongation reaction, can also drive initiation as side reactions. A role for FabB and FabF in the initiation of fatty acid biosynthesis would be supported by the viability of the ΔfabH mutant. In this study, we show that the ΔfabH and ΔyiiD mutations were synthetically lethal and that ΔfabH ΔrelA ΔspoT and ΔfabH ΔdksA synthetic lethality was rescued by the heterologous expression of yiiD. In the ΔfabH mutant, the expression of yiiD was positively regulated by (p)ppGpp. The growth defect, reduced cell size, and altered fatty acid profile of the ΔfabH mutant and the growth defect of the ΔfabH ΔfabF fabB15(Ts) mutant in oleate- and palmitate-supplemented medium at 42°C were rescued by the expression of yiiD from a multicopy plasmid. Together, these results indicate that the yiiD-encoded function supported initiation of fatty acid biosynthesis in the absence of FabH. We have renamed yiiD as fabY. IMPORTANCE Fatty acid biosynthesis is an essential process conserved across life forms. β-Ketoacyl-ACP synthases are essential for fatty acid biosynthesis. FabH is a β-ketoacyl-ACP synthase that contributes to the initiation of fatty acid biosynthesis in Escherichia coli. In this study, we present genetic and biochemical evidence that the yiiD (renamed fabY)-encoded function contributes to the biosynthesis of fatty acid in the absence of FabH activity and that under these conditions, the expression of FabY was regulated by the stringent response factors (p)ppGpp and DksA. Combined inactivation of FabH and FabY resulted in growth arrest, possibly due to the loss of fatty acid biosynthesis. A molecule(s) that inhibits the two activities can be an effective microbicide.

Autoimmune hemolytic anemia (AIHA) is a very rare cause of anemia in a case of malaria and drug-induced AIHA is even rarer. A 50-year old patient with a history of fever for 8 days was diagnosed with a case of complicated malaria with mixed infection having initial parasite index of 45%. He showed good response on initial therapy with artesunate (parasite count reduced to <1%) but his haemoglobin (Hb) continued to drop from 12 g% to 4.9 g% over a course of 11 days. Direct coombs test was positive with reduced haptoglobin and increased lactate dehydrogenase suggesting AIHA. The patient was put on steroids and transfused with saline washed O-negative blood. He gradually recovered over 8 weeks with Hb level rising up to 12 g%. This is a rare case of AIHA following treatment of severe malaria with parenteral artesunate suggesting of the drug immune-related mechanism.

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Leptospirosis is an important re-emerging infectious disease. Leptospirosis has been estimated to affect tens of millions of humans annually with a case fatality rate ranging from 5% to 25%; however, it is underreported due to the lack of clinical suspicion and barriers to diagnostic capacity. A 33-year-old healthy male presented with a history of fever of 2-day duration. His examination revealed icterus. His workup did not show any significant findings except for a mild transaminitis and a rise in serum creatinine by 0.5 mg/dl. Later, the patient developed bradycardia. An ELISA test for Leptospira antibodies was positive. The patient recovered after a course of intravenous antibiotics. Leptospirosis should be considered early in the diagnosis of any patient who presents with acute, nonspecific febrile illness with multiorgan involvement. Our case had an atypical presentation with involvement of the cardiovascular system in the form of junctional rhythm.