Our results suggested that precipitation of different minerals is induced by the different cellular envelopes of the different bacteria found in this study.
This finding might be explained as follows: The cellular envelopes of either type of bacteria differ dramatically and the outer membrane of the Gram-negative cells with its lipopolysaccharide leaflet might pose an impermeable barrier for the methanol-extractable Rhododendron-derived bioactive compounds.
Other bacteria, which, like the symbiont, are thought to be obligately intracellular [ 17], have lost genes required for the production of a cellular envelope, transport of solutes across the plasma membrane, sensing of the extracellular environment, as well as motility.
The variability of clonal lineages at the level of cellular envelope is a well-documented phenomenon and is considered to reflect the interplay between archaeal and bacterial cells and their viral predators [ 10, 14, 52– 52].
mymA is an important operon of M.tb due to its involvement in the remodeling of the cellular envelope under stressful conditions and in the intracellular survival of the pathogen [8], [9], [10].
Therefore, the symbiont of S. velum may not only be able to make a fully functional cellular envelope and supply some of its components to its host, but may also be capable of living outside the bacteriocytes.
The outermost layer of the cellular envelope in Gram-negative bacteria is a layer of self-assembly proteins, as illustrated in Fig. 2b, which is known as a surface layer (S-layer) protein [13].
BCAM1679 encodes a putative lysylphosphatidylglycerol (Lys-PG) synthetase which adds lysine to PG, thereby lowering the net negative charge of the cellular envelope, already lowered in B. cenocepacia by the constitutive presence of 4-amino-4 deoxy-L-arabinose linked to lipid A [ 59].
However, the symbionts which have the genes to synthesize LPS tend to either live directly in the cytoplasm [ 97] and have to make their own cellular envelope or, like the symbionts of R. pachyptila[ 98], exist extracellularly for part of their life.
