SummaryMycobacterial genomes contain two unique gene families, the so-called PE and PPE gene families, which are highly expanded in the pathogenic members of this genus. Here we report that one of the PPE proteins, i.e. PPE41, is secreted by pathogenic mycobacteria, both in culture and in infected macrophages. As PPE41 lacks a signal sequence a dedicated secretion system must be involved. A single gene was identified in Mycobacterium marinum that showed strongly reduced PPE41 secretion. This gene was located in a gene cluster whose predicted proteins encode components of an ESAT-6-like secretion system. This cluster, designated ESX-5, is conserved in various pathogenic mycobacteria, but not in the saprophytic species Mycobacterium smegmatis. Therefore, different regions of this cluster were introduced in M. smegmatis. Only introduction of the complete ESX-5 locus resulted in efficient secretion of heterologously expressed PPE41. This PPE secretion system is also involved in the virulence of pathogenic mycobacteria, as the ESX-5 mutant of M. marinum was affected in spreading to uninfected macrophages.

This study investigated the effect of treated wastewater (TWW) irrigation on growth of Chinese cabbage and corn and on soil properties in Gaza Strip, Palestine. Chinese cabbage and corn were planted in winter and summer seasons respectively in a sandy soil. The experimental design was a randomized complete block using 2 treatments with 4 replicates. Soil samples were collected from 0.0 -120 cm depths from all plots and analyzed for pH, electric conductivity (EC) and nutrient contents. The plants were irrigated with either TWW or fresh water (FW) fortified with NPK, while control used drip irrigation system. The biomass (total fresh weight of the plants) was used as an indicator of the plant yields. Concentration of heavy metals on plant leaves was determined by Inductive Coupled Plasma Analyzer (ICP) and was taken as an indicator of plant quality. Biomass of Chinese cabbage and corn grown in plots irrigated with TWW was higher than those grown in plots irrigated with FW. These results indicate the ability of TWW supplying the necessary nutrients for plant growth. Heavy metal content in plant leaves in all treatments (TWW and FW) was nearly similar and below EPA standards, indicating high quality of plants. Soil analysis showed great changes in soil properties due to irrigation with TWW. The interesting outcome of this study is that TWW is an effective source for plant nutrients. It is encouraging to reuse TWW in agricultural system after full treatment.

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