## 2 Results
On this medium, which reflects a permeability \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Growth Conditions**} \\ \hline
**Gene** & **LA 43 \({}^{\circ}\)C** &
\begin{tabular}{c} **MacConkey** \\ **Agar 37 \({}^{\circ}\)C** \\ \end{tabular} & \(\Delta\)_lapD_ & **Function** \\ \hline _yfgM_ & + & + & + & FtsH substrate, ancillary SecYEG translocon subunit \\ _dksA_ & + & + & + & RNA polymerase-binding transcription factor \\ _artl_ & + & + & + & L-arginine ABC transporter periplasmic binding protein \\ _acpP_ & + & + & + & acyl carrier protein \\ _accB_ & + & - & + & biotin carboxyl carrier protein \\ _lapD_ & + & ND & + & LPS assembly protein \\ _pldA_ & + & - & - & outer membrane phospholipase A \\ _marA_ & + & \(\pm\) & - & DNA-binding transcriptional dual regulator \\ _vecl_ & + & - & - & putative cytochrome b561 \\ _gnsA_ & + & - & - & putative phosphatidylinositolamine synthesis regulator \\ _ymgG_ & + & - & \(\pm\) & PF13436 family protein toxin-antitoxin system \\ _srrA_ & + & + & + & transcription (stress response regulator \(\Delta\)) \\ _acpT_ & + & + & - & _holo_-(acyl carrier protein) synthase 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Identification of the multicopy suppressors of _lapC190_ bacteria that restore the growth at high temperatures and on MacConkey agar. phenotype, a modest suppression is also conferred by the overexpression of _dksA_, _acpP_ and _acpT_ genes (Figure 3). Noteworthy of these suppressor-encoding genes is the isolation of a set of genes (_srrA_, _dksA_, _acpP_, _yfgM_, _ymgG_, _artJ_ and _accB_) whose overexpression was earlier shown to suppress the Ts phenotype of _\(\Delta\)lapD_ bacteria [28]. Such results suggest that some common defects in bacteria that are either lacking the periplasmic domain of LapC or when LapD is absent, can be rescued by overexpression of this set of genes (Table 1). However, the identification of _marA_ and _pldA_ genes is interesting, and their overexpression only suppresses the Ts phenotype of _lapC190_ bacteria but not of \(\Delta\)_lapD_ (Table 1). MarA (multiple antibiotic resistance) is a well-characterized transcriptional regulator, known to regulate the expression of several genes whose products are required for antibiotic resistance, oxidative stress and heavy metals tolerance [32; 34; 35]. Similarly, overexpression of the _acpT_ gene only suppresses the Ts phenotype of _lapC190_ bacteria but not of the \(\Delta\)_lapD_ bacteria. Thus, although some suppressors identified in this work are common to _\(\Delta\)lapD_ and _lapC190_, the overexpression of some genes such as _marA_, _pldA_ and _acpT_ is unique for overcoming the Ts phenotype of only _lapC190_ bacteria, suggesting a partial overlap in the function of LapC and LapD and not all interacting partners could be the same. These conclusions draw further support from results showing that while in multicopy the _lapD_ gene can suppress the Ts phenotype of _lapC190_ bacteria (Figure 4), but in converse, overexpression of the _lapC_ gene does not rescue the Ts phenotype of \(\Delta\)_lapD_ bacteria. Figure 3: Overexpression of specific genes, including _marA_, _srrA_ and _acpP_ genes, restore the growth of _lap190_ bacteria at 43 \({}^{\circ}\)C. Overexpression of some of them, such as _srrA_ (**A**) and _yfgM_ (**B**), also restore growth on MacConkey agar. Growth of isogenic cultures of _lap190_ bacteria transformed with either plasmid DNA of the vector alone or when the specific multicopy suppressing gene is present on the plasmid was quantified by spot dilution on LA 30 \({}^{\circ}\)C and 43 \({}^{\circ}\)C. For the restoration of growth on MacConkey agar, plates were incubated at 37 \({}^{\circ}\)C (**A**,**B**). The relevant genotype and temperature of incubation are indicated.