Bacterial recognition by PGRP-SA and downstream signalling by Toll/DIF sustain commensal gut bacteria in Drosophila

The gut sets the immune and metabolic parameters for the survival of commensal bacteria. We report that in Drosophila, deficiency in bacterial recognition upstream of Toll/NF-κB signalling resulted in reduced density and diversity of gut bacteria. Translational regulation factor 4E-BP, a transcriptional target of Toll/NF-κB, mediated this host-bacteriome interaction. In healthy flies, Toll activated 4E-BP, which enabled fat catabolism, which resulted in sustaining of the bacteriome. The presence of gut bacteria kept Toll signalling activity thus ensuring the feedback loop of their own preservation. When Toll activity was absent, TOR-mediated suppression of 4E-BP made fat resources inaccessible and this correlated with loss of intestinal bacterial density. This could be overcome by genetic or pharmacological inhibition of TOR, which restored bacterial density. Our results give insights into how an animal integrates immune sensing and metabolism to maintain indigenous bacteria in a healthy gut.

Potency of Indigenous Bacteria of Mt. Merapi, Arthrobacter chlorophenolicus for Chromium (VI) Bioremediation

Chromium (VI) in the production process, such as textile, tannery, and electroplating industry, produce hazardous waste when disposed of directly into the aquatic environment. Several chromium pollutions cases, not only in water but also in the aquatic organism, occurred in some regions in Indonesia. Various methods can reduce the Chromium (VI) waste. One of them is the biological method by employing such kinds of bacteria. Arthrobacter chlorophenolicus is a pioneer bacterium of Mt. Merapi, which can survive in the minimum conditions of the bacterial primary nutrients, carbon, and nitrogen. This study aims to investigate the ability of A. chlorophenolicus to remove Cr (VI) at various concentrations. The research was carried out by growing the A. chlorophenolicus into two nutrient media conditions, minimal and rich-nutrient media containing different concentrations of Cr (VI) (5, 10, 20 ppm) for eight days. The results showed that the A. chlorophenolicus were grown on both minimal and rich-nutrient media. The A. chlorophenolicus could reduce for about 80% of 10 and 20 ppm chromium in eight days. Our results indicate that A. chlorophenolicus, the pioneer bacteria of Mt. Merapi, has a grand promise for use in Cr (VI) remediation even under minimum nutrients conditions.

The effectivity of Biduri combined with indigenous bacteria in mercury absorption

Heavy metals pollution, especially Mercury (Hg), is one of the most serious environmental problems. The presence of excessive Hg will cause soil degradation and threaten the life of the ecosystem, for that remediation is necessary. Biduri is known to be able to absorb heavy metals, but there is no research on the ability of Biduri in absorb Hg. The use of indigenous bacteria is expected to increase the absorption of Mercury by Biduri. The purpose of this study was to determine the potential of Biduri combined with indigenous bacteria and Agrobacterium sp I37 in absorbing of Hg in the soil. The experimental was designed as factorial with completely randomized design, consisting of 2 factors namely Bioremediation agent (A0: without bioremediation agent, A1: indigenous bacteria, A3: Agrobacterium sp I37) and Hg dosage (D0: without Hg, D1: Hg 0.3 µg.g-1, D2: Hg 0.51 µg.g-1). The results showed that the combination of Biduri with indigenous bacteria + 0.3 µg.g-1 Hg shows highest absorption of Hg at 57.19 µg (99.24% higher than control) and reduce soil Hg levels by 0.09 µg.g-1. Biduri is a hyperaccumulator plant because it is able to absorb more than 10 µg.g-1 of mercury.